Which sentence best explains how the use of metaphor in the excerpt supports baldwin's purpose?

.By suggesting that hatred is a disease that can manifest itself at any time, it shows how pervasive hatred can be.

If this is the missing excerpt:
That year in New Jersey lives in my mind as though it were the year during which, having an unsuspected predilection for it, I first contracted some dread, chronic disease, the unfailing symptom of which is a kind of blind fever, a pounding in the skull and fire in the bowels. Once this disease is contracted, one can never be really carefree again, for the fever, without an instant's warning, can recur at any moment.

If these are the missing choices:
A.By using a description of hatred that appeals to the senses, it helps readers better imagine the effects of hatred.
B.By describing the author's experience with a similar disease, it implies that hatred is contagious.
C.By suggesting that hatred is a disease that can manifest itself at any time, it shows how pervasive hatred can be.
D.By implying that no one is immune to the symptoms of racial hatred, it shows that everyone has the capacity to hate.

My answer is: 
C.By suggesting that hatred is a disease that can manifest itself at any time, it shows how pervasive hatred can be.

This line clinched my  
Once this disease is contracted, one can never be really carefree again, for the fever, without an instant's warning, can recur at any moment.

Once you experience hate, there is always a time that said hatred will resurface. One can't control when it will appear because it always takes one by surprise.