A verb form question gives you forms of one verb and tests whether the sentence is complete. Sort the forms by their jobs: a main verb says what the subject does or is, while -ing, to, and having forms can't do that alone. Find the subject in the sentence with the blank, then read to the period and count its main verbs. If none belongs to that subject yet, the blank needs to add one.
Hints
- Hint 1
Start with the second sentence and find its subject, the thing the sentence is about.
- Hint 2
Read to the period and check who does the surviving. Does survive say what the endospore does, or what the bacterium does?
Step-by-step
Sort the forms, then count main verbs
Step 1Find the subject and sort the forms
Start with An endospore, the subject, the thing the second sentence is about. Does this subject still need a main verb, a verb that says what it does or is? Let's sort the forms by job: an -ing, to, or having form can't be a main verb on its own.
- Step 2
Check who does the surviving
Read through a bacterium survive periods of extreme heat or dryness. Who does the surviving? It's the bacterium, so survive can't be counted as the endospore's main verb. The first sentence's verbs belong to that sentence; they don't complete the second one. The blank is the only place left for the endospore's main verb.
- Step 3
Add the main verb
Which form can fill that main verb slot? The main verb form is helps, which tells us what An endospore does. It works as a main verb without a helper, and its singular form matches the one endospore in the sentence. Choice C.