An agreement question tests whether you can match a verb to its true subject. Sort the forms by number: one thing takes a singular verb, and more than one takes a plural verb. Then find the verb’s true subject by asking who or what the verb is about. If the blank follows an opening phrase without a comma, look after the blank and try putting the subject first. A nearby noun may belong to a phrase instead of being the subject.
Hints
- Hint 1
Look at the words on both sides of the blank. Does the opening phrase name the subject, or tell us what group the subject belongs to?
- Hint 2
Try moving the subject to the front. Ask what belongs among the measurements that guide thinning.
- Hint 3
Set the phrases about stiffness and mass aside while you check the main noun with it or they.
Step-by-step
Find the subject in reversed order
Step 1Sort by number
Start by sorting are, have been, and were as plural forms, since each works with they, not it. The sentence needs a verb that matches its true subject, so number matters before tense. The plural noun in Among the measurements is close to the blank, but we still need to find out whether it controls the verb.
- Step 2
Find the subject after the verb
Among the measurements that can guide the final rounds of thinning runs straight into the blank without a comma. The words about guiding the thinning describe the measurements, so they stay inside that opening phrase. What belongs among those measurements? The ratio named after the blank answers that question, so the subject follows the verb. Flip the order to check: the ratio of the soundboard’s stiffness to its mass _____ among the measurements.
- Step 3
Shorten the subject
The words of the soundboard’s stiffness to its mass tell us which ratio we mean, not how many ratios there are. What remains when we set that phrase aside? The subject’s main noun is the ratio, and a value later describes that same ratio rather than adding another one. One ratio takes a singular verb, even though it compares stiffness and mass.
- Step 4
Match the verb
Which form goes with it? We say it is, so is gives us the singular verb for the ratio, even though that subject comes after the blank. Choice C.