Your best choice is B, opposite of the word hamper. If you suppose someone, you are trying to help them. If you hamper them, you are trying to stop them from doing something.
So A is wrong.
C is also incorrect. If they are opposite in meaning, one of the words will not define the other.
D is nonsense. As an answer it has no meaning. Parts of speech means verbs and nouns and pronouns etc. None of them are supports.
