Question 135·Hard·Form, Structure, and Sense
Despite numerous studies on urban biodiversity, the loss of green corridors in major metropolitan areas, along with the decline of community-managed gardens, ______ scientists’ understanding of how city planning affects migratory birds.
Which choice completes the text so that it conforms to the conventions of Standard English?
For Standard English subject–verb agreement questions, first strip away introductory phrases and extra modifiers (such as those starting with “along with,” “as well as,” or “in addition to”) to isolate the true subject. Decide if that subject is singular or plural, then immediately eliminate any answer choices whose verbs do not match in number. Finally, check which remaining tense (simple, perfect, progressive) best fits the time relationship implied by the sentence, focusing on whether the action is completed, ongoing, or has present results.
Hints
Locate the main clause
Mentally cross out the intro “Despite numerous studies on urban biodiversity,” and focus on the part that starts with “the loss of green corridors…” That’s where the subject and verb you’re choosing belong.
Decide if the subject is singular or plural
Look carefully at the structure: is “along with the decline of community-managed gardens” part of a compound subject, or is it extra information added to the main subject “the loss of green corridors”?
Use subject–verb agreement to narrow choices
Once you know whether the subject is singular or plural, eliminate any choices that use the wrong form of the verb (singular vs. plural).
Check which tense fits the meaning
Ask yourself: does the sentence describe something that has already affected scientists’ understanding up to now, or something that is happening right this moment? Pick the tense that best fits that idea.
Step-by-step Explanation
Find the main subject and verb position
Ignore the introductory phrase starting with “Despite numerous studies on urban biodiversity,” because that is just a modifier. The core sentence begins at “the loss of green corridors in major metropolitan areas, along with the decline of community-managed gardens, ______ scientists’ understanding…” You are choosing the verb that completes this main clause.
Identify the true subject of the sentence
The main subject is “the loss of green corridors in major metropolitan areas.” The phrase “along with the decline of community-managed gardens” is extra information (like a side note) and does not change the subject from singular to plural. So the subject is singular: loss.
Match the verb to a singular subject
Because the subject “loss” is singular, the verb must also be singular: has (not have). This immediately rules out any option that uses have as the main verb form for this subject.
Choose the correct tense and aspect
Now compare the remaining singular forms: a simple present progressive like “is complicating/are complicating” versus a present perfect like “has complicated.” The sentence describes an existing condition that has already made scientists’ work more difficult up to now. The present perfect (“has complicated”) matches this idea of a past action with present results better than the ongoing-action feeling of the progressive.
Therefore, the correct answer is “has complicated” (Choice B).