ACT English practice test

The cameras belong to one remotely operated vehicle, so vehicle’s is the correct singular possessive.

The sentence identifies the hydrophone as an underwater microphone and states that it records the reef’s soundscape, so deleting it would remove the explanation of the tool used to collect the recordings discussed in the paragraph. It does not relate the hydrophone to the cameras, describe the recognizable sound pattern introduced later, or interpret what the sounds indicate about reef health.

“The sounds are distinct” states the contrast without repeating individual, separate, and others.

Bell’s need to identify a meaningful pattern leads her to compare recordings systematically, a cause-and-effect relation signaled by “For that reason.” “In comparison” and “Nevertheless” imply contrast the passage does not make, and “For example” wrongly treats the comparison as an illustration rather than the next step.

“Decrease” most clearly conveys that the high clicks have become less frequent. “Departure” (NO CHANGE) means leaving or a deviation, not a reduction in number. “Distortion” describes a change in quality rather than quantity, and “distance” refers to space, not a decline in clicks.

Matching each recording to a location should follow review of the navigation log and precede comparison of the samples, so the sentence belongs at Point B. Point A is too early because the team has not yet consulted the log. Point C places the matching after the comparison, contradicting “Only then.” Point D comes after “This location record,” which needs the matching sentence as its antecedent.

“Whereas” correctly makes the camera clause subordinate and establishes the contrast, avoiding the original comma splice.

The introductory phrase between the subject and verb must be closed with a comma.

The findings belong to more than one researcher, so the possessive needs an apostrophe after the plural noun: researchers’. The noun findings is a plain plural and takes no apostrophe. NO CHANGE leaves out the possessive. B makes researcher singular and adds an apostrophe to findings. D leaves researchers without a possessive and wrongly makes findings possessive.

The original reflects the passage’s central goal of testing whether quieter recordings can warn of reef stress before visible damage appears; the other choices are plausible aims involving nearby study details but are not Bell’s stated goal.

The colon correctly introduces examples of the small events after a complete clause. The semicolon and period leave the examples as a sentence fragment; “events that include:” incorrectly places a colon between a verb and its objects.

The plural subject “Those notes” requires the plural verb “help,” despite the intervening phrase about boats. “Now helps” and “does now help” use singular verbs, while “now helping” leaves the sentence without a main finite verb.

“Deliberately plain” conveys both simplicity and intention without repetition. “In a way that is intentional” repeats “deliberately,” “deliberate and intentional” duplicates the same idea, and “on purpose” repeats “deliberately.”

No punctuation should separate the subject “a stone dropped at the usual crossing” from its verb “rests.” The comma incorrectly divides that subject from its verb, the semicolon does not join independent clauses, and the colon follows an incomplete clause.

“Likewise” connects two examples of defining seasonal changes through observable events rather than feelings. “Nevertheless” incorrectly signals a concession, “therefore” implies that the freezing criterion causes the thaw criterion, and “instead” presents the thaw criterion as a replacement for the freezing criterion.

Chart most precisely expresses mapping the events’ locations and timing using the stations’ observations. Recount means narrate, and infer means deduce; neither specifically expresses mapping the observed progression. The original ‘track freeze-up and breakup along the river’ indicates monitoring but is less precise about mapping the events’ locations and timing.

Suggest allows the photograph to create an impression that the logs contradict. Confirm treats that impression as verified, and explain presents an account of how or why it occurred. The original ‘give an impression of winter’s end’ does not specify the misleading impression of simultaneous breakup.

The existing conclusion connects a finely detailed record with the ability to detect small changes in the season over time. The account of winter’s stages describes observations without explaining their long-term significance; the sentence about towns emphasizes immediate practical uses instead. The sentence about steamer captains emphasizes the tradition’s origin without connecting precision to the understanding of change.

The essay explains the collection and value of evidence but does not identify causes of the shorter frozen season. Mentioning hydrologists’ investigation does not explain its findings, and describing the geographic progression of a thaw does not explain a long-term shortening. The claim that the records have only historical uses contradicts the discussion of hydrologists and present-day towns.

The comma after “disturbance” closes the description beginning “a single-celled dinoflagellate,” leaving “Pyrodinium bahamense produces” as the sentence’s main structure. The original leaves that description open, and the semicolon separates material that cannot stand as two independent clauses. “Producing” removes the main clause’s finite verb, creating a fragment.

Prompting already concentrated cells to produce light distinguishes the paddle’s stimulation of a flash from the bay’s retention of organisms. NO CHANGE incorrectly assigns the gathering of cells to the paddle. Making retained light visible confuses retention of organisms with storage of light. Revealing the concentration describes what observers learn but leaves the paddle’s immediate role in causing light production unspecified.

“The conditions that sustain the organisms” anticipates the discussion of circulation, contamination, and storm disturbance. The original and the contrast between surface and wake emphasize the spectacle’s appearance without introducing its ecological requirements. The range of paddle movements would prepare readers for a discussion of paddling techniques that the essay never develops.

Limiting dispersal explains why organisms remain within the bay without claiming complete isolation. NO CHANGE gives that explanation but also anticipates the following sentence’s qualification about continued exchange. The nutrient choice explains population support rather than retention within geographic boundaries. The isolation choice converts restricted exchange into separation from the sea, contradicting the following sentence.

“Nevertheless” qualifies the appealing observation about kayaking by introducing a limit on how visitors should interact with the organisms. “Similarly” incorrectly presents the caution as a parallel observation, while “Consequently” treats it as a result of the preceding statement. “For example” promises an illustration of kayaking’s ability to reveal the glow, which the caution does not provide.

“The restriction” logically performs the action described in “By keeping swimmers out of the water.” In the original, “contact” cannot keep swimmers out. Neither the substances nor the bay’s organisms perform that action, so both remaining alternatives also leave the introductory modifier attached to the wrong subject.

The addition bridges the swimming restriction and the hurricane by widening the discussion beyond visitor behavior. It neither ranks the value of different protective efforts nor contradicts the usefulness of restricting swimming. The paragraph has not yet compared human activity with natural disturbances, so the addition does not repeat such a comparison.

The semicolon correctly joins two independent clauses, with “for a time” introducing the second. Both comma alternatives create a comma splice, even though they attach the time phrase differently. Adding “which meant that” makes the material after the semicolon dependent rather than an independent clause.

The original sentence distinguishes an observed loss of light from permanent loss of the habitat’s capacity to support the organisms, preparing readers for recovery without inventing its mechanism. The claim that organisms survived but temporarily stopped producing light supplies an unestablished biological explanation. The claim that mangroves had to recover fully imposes an unsupported prerequisite. The comparison of mangroves with circulation assigns relative importance that the paragraph’s evidence cannot establish.

Recognizing continuing vulnerability carries forward the hurricane account’s distinction between visible recovery and demonstrated resilience. NO CHANGE treats renewed light as proof that earlier dependability has returned. Judging protective measures by the returning glow assumes a causal connection the essay does not establish. Making restored brightness the guide for all conservation decisions elevates one visible sign above the broader habitat conditions the conclusion emphasizes.

“A momentary sign of an ecosystem that requires continuing care” links the opening’s brief luminous trail to the final paragraph’s ongoing responsibilities. The original returns only to visual admiration. The alternatives about small organisms and dark backgrounds explain aspects of visibility but do not connect that visibility to sustained protection.

The correct choice closes two nested interruptions: the phrase beginning with “by bringing” ends after “together,” and the description of Leavitt ends after “changes.” NO CHANGE leaves the inner interruption unclosed. The choice with “whose work by bringing” supplies only the inner interruption’s closing comma, separating “work” from “could reveal.” The choice ending with “changes studied” closes the inner interruption but leaves Leavitt’s description unclosed before the main verb.

The correct choice maintains parallel structure at two levels: “organizing” joins “comparing” and “distinguishing,” while “grouping” and “arranging” share the preposition “by.” NO CHANGE pairs “grouping” with the infinitive “to arrange.” The choice beginning with “to organize” repairs the inner pair but breaks the outer series. The choice containing “then arrange” begins the outer series correctly but places a base-form verb alongside “grouping” after “by.”

Showing when a star returned to peak brightness supplies the timing needed to determine its period. NO CHANGE emphasizes the magnitude of brightness changes, whereas a period measures elapsed time. Comparing different stars’ apparent brightness anticipates a separate discussion of intrinsic brightness, rather than period measurement. Preserving images for later examination repeats the opening point without establishing how recurring changes are timed.

NO CHANGE identifies the independence that makes the later process possible: astronomers can measure a period before using it to estimate intrinsic brightness and then comparing that estimate with apparent brightness. The choice about a “calibrated scale” confuses the common-distance assumption with the independent measurement needed for calibration. The choice about “equal intrinsic brightness” makes a conclusion drawn using the relationship a prerequisite for measuring a period. The choice about converting brightness differences into distance differences reverses the later procedure, making its eventual result precede its starting measurement.

The correct choice joins two independent clauses with a semicolon. Within the second clause, the introductory “as” clause precedes the main statement that the stars with longer periods were brighter. NO CHANGE uses only a comma between the independent clauses, despite the intervening “as” clause. The choice containing “showing that” places a fragment after the semicolon: “were” belongs to the embedded “that” clause and supplies no main verb for “comparisons.” The choice containing “showed that” creates a complete second clause but joins it to the first with only a comma.

“Nevertheless” introduces a limitation on the measuring potential described in the preceding sentence. “Consequently” incorrectly presents the limitation as a result of that potential. “In addition” misses the qualifying relationship, while “For example” incorrectly frames the limitation as an illustration of a successful measurement.

The preceding sentence identifies the comparison, and “yielded a distance” already states its result completely. The original restates that result as determining how far away the star was. Both “establishing how far” and “allowing the distance” repeat the same information without adding a qualification.

“Edwin Hubble” correctly identifies the person using the Cepheids in the introductory phrase. The original makes “evidence” the user of the Cepheids. The other replacements incorrectly attach that action to Andromeda or to a distance estimate; merely mentioning Hubble elsewhere does not fix the attachment.

“Organized” describes bringing separate observations into an intelligible pattern. “Regulated” suggests controlling the observations rather than interpreting them. “Synchronized” implies aligning their timing, and “standardized” implies making them conform to a common specification; neither describes the discovery emphasized here.

The essay follows the relationship from the conditions that made it discoverable through calibration and its application to Andromeda. It does not claim that apparent brightness is independent of distance. Leavitt’s not making the later measurements does not prevent the essay from explaining the tool’s development, and the essay explicitly identifies calibration as an additional requirement.

The correct choice closes two nested nonessential elements: the phrase describing the reconstructions and the longer description separating the subject “find” from “contained.” NO CHANGE opens the phrase beginning “tested” without closing it before “continue.” The choice beginning “whose reconstructions tested” places a comma between the subordinate clause’s subject and its verb without opening a parenthetical phrase. The choice ending “develop contained” closes the inner phrase but leaves the description of the find unclosed.

The distinction between accessibility and intelligibility introduces the essay’s account of extracting meaning from recovered fragments. Adding to a collection and providing evidence of cargo emphasize the recovery’s archaeological value without establishing that distinction. Preserving an artifact for examination anticipates research but does not convey the difficulty of understanding it.

The correct choice distinguishes the early identification of an astronomical purpose from the later testing of possible internal arrangements. NO CHANGE reverses the evidentiary relationship: the paragraph presents the scans as evidence for testing reconstructions, not earlier interpretations as a standard for judging the scans. The choice beginning “were features that could establish” incorrectly postpones the identification of function until after scanning. The choice beginning “were features whose relationships” turns additional constraints into a complete resolution, conflicting with the continuing uncertainty described later.

NO CHANGE preserves the distinction between establishing a general purpose and examining concealed evidence about construction. That distinction explains why scanning could advance understanding even after an astronomical purpose was known. The choice beginning “Because that finding depended” makes the earlier finding depend on evidence obtained later. The choice beginning “As researchers revised” invents a revision of the established purpose and places scanning before the paragraph introduces it. The choice beginning “Because that finding made” invents a loss of evidentiary value; the passage instead shows physical clues continuing to constrain reconstructions.

The correct choice joins two independent clauses with a semicolon. The second independent clause begins with a dependent “once” clause, which is properly followed by a comma before “they also exposed.” NO CHANGE uses only a comma between the independent clauses; the intervening dependent clause does not repair that splice. The choice ending “also exposing” leaves the material after the semicolon without an independent clause. The choice with two semicolons incorrectly separates the dependent “once” clause from the main clause it introduces.

The correct choice preserves parallel structure at two levels: “compare” joins “count” and “trace,” while “to test” pairs with “to check” after “both.” NO CHANGE repairs the outer series but incorrectly pairs “to test” with “checking” inside the added description. The choice beginning “comparing” makes the inner pair parallel but disrupts the outer series of actions. The choice containing “required both testing” incorrectly pairs “testing” with “to check.”

“Model” describes representing astronomical cycles through the coordinated movement of mechanical parts. “Observe” and “detect” would imply that the mechanism gathered information directly from the sky. “Regulate” would imply that it controlled the astronomical cycles themselves.

The introductory phrase describes the makers’ action, so “they,” referring to the makers, must be the subject of the following clause. In the original, “patterns” incorrectly occupies that position. Both alternatives beginning their main clauses with “representations” or “the representation” likewise fail to name whoever coordinated the gears.

“How completely” already expresses the extent of reconstruction, making “in its entirety” redundant. “Prevent researchers from reconstructing” changes a limitation on completeness into a claim that reconstruction cannot occur. “Limit researchers who reconstruct” shifts the limitation to the researchers without specifying what aspect of their work is limited.

The essay explains what the combined evidence establishes and distinguishes those findings from unresolved questions about missing parts, the maker, and use. It does not claim that tomography identified the maker or that the gears’ astronomical role remains unknown. A complete inventory of researchers and reconstructions is unnecessary for the stated purpose, and acknowledging missing parts does not make every conclusion equally uncertain.