A verb form question tests whether the blank needs a main verb or a form that adds detail. First, find the subject and main verb in the sentence with the blank. Check each form's job: a main verb must match its subject and connect correctly to any other main verb. An infinitive, to plus a verb, can explain purpose if in order fits before it. Wrong choices often leave a sentence with verbs that don't work together.
Hints
- Hint 1
Read the second sentence through the period and find the verb that tells what the microbiologists do.
- Hint 2
What does the first sentence suggest about why microbiologists apply dyes?
Step-by-step
Count the verbs, then test the purpose
Step 1Find the main verb
Sort the forms by their jobs: saw, sees, and has seen can be main verbs, which say what a subject does or is. Does the sentence need one? In Microbiologists often apply colorful dyes to the bacteria, the subject already has apply as its main verb.
- Step 2
Check whether another main verb is allowed
Is anything there to join a second main verb? After to the bacteria, there's no and joining two things the microbiologists do and no new subject with a verb of its own. So the blank must add a detail, not another main verb, which rules out saw, sees, and has seen.
- Step 3
Test for purpose
Why do the microbiologists apply the dyes? The bacteria are nearly transparent, so the dyes help the microbiologists see details in the cells more clearly. The blank gives the purpose of applying the dyes. Use the in order test by putting those words before to see: they apply dyes in order to see those details. Choice A.