A verb form question with a long opening tests whether you can find the subject and main verb. Sort the forms: -ing forms need helpers to be main verbs, while to forms can't be main verbs. Then read through the period, checking which subject each verb belongs to. If the blank needs a main verb, match the whole subject: one thing takes a singular verb, and more than one takes a plural verb. A nearby noun may not be that subject.
Hints
- Hint 1
Read from That through plurality. What do those words name as a whole?
- Hint 2
Look for a main verb outside the opening words. Set aside the phrase naming Okafor and treat the words after the colon as a separate explanation.
- Hint 3
Test the whole opening with it or they. Which replacement keeps the meaning of all the words from That through plurality?
Step-by-step
Sort, count, and match
Step 1Sort the verb forms
The choices mix main-verb forms with constituting and to constitute, which can't be main verbs on their own. A main verb says what the subject does or is, so sort the forms by whether they can do that job. Then start at That several independently developed writing systems and read to the period.
- Step 2
Find the whole subject
Which words are the subject? That several independently developed writing systems use repeated signs to indicate plurality names a fact, not a collection of writing systems. The verb use says what the systems do inside those words, so it isn't the main verb of the larger sentence. The whole fact is the subject, and it counts as one thing even though it contains the plural noun systems. We can shrink the opening to that fact or it.
- Step 3
Check for a main verb
according to historical linguist Amara Okafor names the source, so set it aside. Does anything else before the colon already say what that fact is? The remaining words describe the evidence but supply no main verb. The later can be more efficient belongs to the explanation after the colon, not to the opening subject. So the blank must supply the missing main verb.
- Step 4
Match the verb to one fact
Which main-verb form works with it? Constitute would give it constitute evidence, which doesn't work because one fact needs a singular verb. Constitutes gives it constitutes evidence, meaning that the fact counts as evidence. Choice B.