Whom is correctly used as the object of a verb.
true or false?

It is true.

Explanation:

Many English speakers know the pronouns "who" and "whom" are not the same, but don't really know when to use which. "Who" should be used to refer to the subject of a sentence, while "whom" should refer to the object of a verb or preposition. A trick is to think the following: if you can substitute it for a subject pronoun (he, she...), then it should be "who"; if you can do it for an object pronoun (him, her...), it should be "whom". Note the examples below:

- That is the man who helped me cross the street. --> That is the man. He helped me cross the street. (subject)

- That is the man whom I helped cross the street. --> That is the man. I helped him cross the street. (object)

the correct answer would be:  

a. adverb phrase

the answer is c because info security should not use them for code