An agreement question tests whether a verb matches its subject: one thing takes a singular verb, and more than one takes a plural verb. Sort the choices by number, keeping -ing forms apart. Read the sentence to check for a main verb, which says what its subject does or is; an -ing form alone can't be one. Then find the true subject by asking who or what does the verb's job, and check the forms with it or they.
Hints
- Hint 1
Read the last sentence all the way to the period. What does the verb moved tell us about?
- Hint 2
Find the subject of the blank's verb. Would you replace that subject with it or they?
Step-by-step
Sort, check, and match
Step 1Sort the verb forms
Sort the forms for The cluster ______: indicate and have indicated go with a plural subject, meaning more than one thing. What about indicating? Without a helper like is, it can't be a main verb, the verb that says what a subject does or is. So check whether the blank needs a main verb.
- Step 2
Check for the missing main verb
Read that the bacteria moved toward a food source. Does the verb in that part already give the cluster a main verb? It tells us what the bacteria did, while the whole part tells us what the cluster shows. No verb yet says what the cluster itself does, so the blank needs a main verb, which rules out indicating.
- Step 3
Match the singular subject
What shows that the bacteria moved toward food? The cluster is the subject, one group even though it contains many cells. Replace the subject with it: one group takes a singular verb, so indicates works in the short check it indicates. Choice C.