What is the incorrect verb of this sentence

The novel begins with a flashback. what do you think is its purpose? what do you learn about the narrator?

Which of the following sentences below uses the simplest and clearest language? a. library cards are not too hard to get, but they aren't too easy to get either. b. some libraries have a lot of rules to follow for filling out the forms. c. library cards make it possible to read books all year long. d. once you get the application, you can figure it out.

When the subject of a sentence performs the action in the sentence the verb in the sentence is in the what ?