What is the meaning of the idiom "to swallow something hook, line, and sinker"?

When you say, "to swallow something hook, line, and sinker" it means to completely fall for whatever was said or to completely believe what was told or presented. Usually, what was presented is a lie, and when the person is gullible enough to believe it, the phrase applies.

it is an infinitive phrase with a subject.

the answer is academic paper

and the second should be college professor