A verb agreement question tests whether a verb matches a subject that names one thing or more than one. Sort the helper verbs by whether they fit it or they, then find the true subject. If extra phrases add nouns, ask whether those nouns join the subject or give extra information. Two subjects joined by and take a plural verb; phrases that add extra information don't change which verb the subject needs. A nearby noun can belong to a phrase rather than be the subject.
Hints
- Hint 1
Look for the subject of the blank's verb by asking what prompted the government to change its export regulations.
- Hint 2
Check what as well as does between the commas. Does it join two subjects in the same way and would, or add extra information?
- Hint 3
Once you've set aside the added phrases, test the main noun with it or they. Which pronoun stands for that noun?
Step-by-step
Find the true subject
Step 1Sort the helpers
Start by sorting the helpers in the choices by whether they fit it or they. In have, were having, and are having, the helpers fit they, so those helpers need a plural subject. The blank completes the verb ending in prompted the government to revise its export regulations, which means we need the true subject of that verb.
- Step 2
Set aside the researchers
Does as well as the researchers who documented them make the researchers part of the subject? It doesn't, because as well as adds extra information, unlike and, which can join two subjects into a plural subject. The commas also show that this phrase can be set aside while we find the subject. So the researchers don't decide which verb the subject needs, even though they name more than one person and sit close to the blank.
- Step 3
Remove the describing phrase
What noun is left once we remove the phrase about the researchers? The opening noun is The abundance, and of rare earth minerals discovered in the region describes what is abundant. We can cross out that of phrase because abundance is the subject, not the plural noun minerals inside the phrase.
- Step 4
Match the singular subject
Does The abundance count as one thing or more than one? It names one amount, so we can shrink the subject to it. Has is the singular helper, giving us it has prompted and completing the verb in the original sentence. Choice D.