MISANTHROPE: HUMANITY∷

Misanthrope is someone who hates the whole humanity.
The second word given is humanity. Thus, the relation between the given words is - 1st word will describe the hate for the second word.
Among the given option only option B satisfies this condition and is thus the right answer.
In Chauvinist: Patriot here Chauvinist is someone who expresses aggressive patriotism and thus is opposite of our condition.
In Agnostic: God, Agnostic is someone who believes that there is no proof that God does not exist. This does not mean he hates God he just doubts his existence. Thus, this is not the right answer.
Witch: Magic  is exactly opposite of our condition and hence cannot be the right answer.
Hence, option B is the correct answer.