A verb form question tests whether a sentence needs a main verb and which form matches its subject. Sort the forms: an -ing or to form can't be a main verb on its own. Find the subject, then read to the period for any main verb already there. If one is missing, match the true subject: one thing takes a singular verb, and more than one takes a plural verb. Nearby nouns don't decide the verb.
Hints
- Hint 1
Read the second sentence all the way to the period and look for a main verb outside the blank.
- Hint 2
Set aside the phrases beginning with of and near, then check whether the subject is singular or plural.
Step-by-step
Find the main verb, then match its subject
Step 1Check whether the sentence has a main verb
Read the performance sentence all the way through the instrument’s pitch and volume. Does any word outside the blank serve as its main verb, the verb that says what the subject does or is? No, so the blank must supply a main verb for the sentence to be complete. The forms controlling and to control can't be main verbs on their own, so both leave the sentence unfinished.
- Step 2
Find the true subject
Which word names the subject of the missing verb? It's the position; of a musician’s hands near two metal antennas tells us which position we mean. The hands and antennas are in those added details, so they don't decide the verb's form. One position is a singular subject, meaning it names one thing.
- Step 3
Match the verb to one position
Use it for the subject: which main-verb form can follow it? The form have controlled has the plural helper have, so it doesn't match the position. With controls, we get it controls, which supplies the singular main verb this sentence needs. Choice B.