Question 182·Medium·Form, Structure, and Sense
Wildlife biologist Mara Simmons has spent years studying how urban noise pollution affects songbirds. In her latest study, she discovered that sparrows living near busy highways sing louder and at higher pitches, a behavioral change that ______ them to communicate effectively over background noise.
Which choice completes the text so that it conforms to the conventions of Standard English?
For relative clause questions like this, first locate the noun that the relative pronoun (“that,” “who,” “which”) refers to; that noun is the subject of the verb in the clause. Check subject–verb agreement by deciding if that noun is singular or plural, then eliminate choices that don’t match in number. Finally, make sure the remaining verb fits the sentence’s time frame (general present, past action, etc.) and keeps the clause fully grammatical—not just a participle hanging after “that.”
Hints
Notice the phrase starting with “that”
Look at the words right before the blank: “a behavioral change that ______ them…” Think about what the word “that” is referring to and how it affects the verb form.
Figure out the subject for the verb in the blank
Ask yourself: Is the subject inside the “that” clause singular or plural? Which noun is actually doing the action described in the blank?
Check verb form and tense
Once you know if the subject is singular or plural, eliminate any verbs that do not match in number. Also think about whether the sentence is describing a general, ongoing fact or a completed past event.
Step-by-step Explanation
Locate what the blank is doing in the sentence
Focus on the part around the blank: “a behavioral change that ______ them to communicate effectively over background noise.”
The word in the blank is a verb inside a clause that starts with “that.” It tells us what the “behavioral change” does.
Identify the subject of the verb in the blank
Ask: What does “that” refer to? It refers to “a behavioral change.”
So inside the clause, the subject is “a behavioral change,” which is singular. The verb in the blank must agree with this singular subject.
Check which choices agree in number and fit the clause structure
Now test each option after “that”:
- “that allow them…” → uses a plural verb, which does not agree with the singular subject “change.”
- “that allowing them…” → “that” is followed by a participle, not a full verb, breaking the clause structure.
- “that has allowed them…” → is a full verb, but uses a perfect tense that suggests a completed action, not a general ongoing effect like the rest of the description.
We need a singular simple present verb that follows “that” and matches the general present description of how the change works.
Select the verb that matches subject and tense
The only option that is a singular, simple present verb that fits after “that” and agrees with “a behavioral change” is “allows.”