A subject-verb agreement question tests whether a verb matches its subject despite phrases between them. Sort the choices by one thing or more than one, checking the helping verb in forms with several words. Then cross out phrases that only add details to find the verb’s true subject. One thing takes a form that works with it, while more than one takes a form that works with they. The nearest noun may be inside an added phrase.
Hints
- Hint 1
Look at the part after the opening phrase about studies. What does the sentence say is complicating scientists’ understanding?
- Hint 2
In the part before the phrase about gardens, cross out the phrases beginning with of and in. What remains?
- Hint 3
The phrase beginning with along with is set off by commas. Check whether it adds a subject or extra information, then try it or they for the subject you found.
Step-by-step
Sort, find, and match
Step 1Sort by number
Sort the verb forms that go before scientists’ understanding by number. This question tests subject-verb agreement, which means the verb’s form depends on whether its subject is one thing or more than one. The helping verbs have and are work with they, so those forms are plural. Start with number rather than tense, then find what is complicating scientists’ understanding.
- Step 2
Find the main noun
Look past Despite numerous studies on urban biodiversity, which gives background rather than the subject. What does the sentence say is complicating that understanding? In the loss of green corridors in major metropolitan areas, the of phrase tells us what’s being lost, and the in phrase tells us where. Cross out those details, and loss is the main noun.
- Step 3
Check the added garden phrase
Does along with the decline of community-managed gardens add a second subject? No: along with adds extra information, here set off by commas; it doesn’t join subjects the way and does. The sentence mentions two changes in the city, but only the loss is the subject of the verb in the blank. Cross out the whole garden phrase, so the subject stays singular.
- Step 4
Match the helping verb
Replace the loss with it and test the short sentence. Which helping verb works with that pronoun? We say it has complicated, so has is the matching helping verb and has complicated is the form the sentence needs. Choice B.