Nodding your head should be added to which statement/question?

a). who is your brother?
b). recently, i took an american sign language course.
c). yes, i agree.
d). no, i don't think so.

To me, the answer that makes the most sense with this gesture is C.). Yes, I agree.

'parallelism  in grammar is defined as two or more phrases or clauses in a sentence that have the same grammatical structure.'c. he was not a beast, but he was not a man. 

•as parts of ceremonies and often to ask for peace and blessings from evil. • late at night to entertain themselves or foreign visitors at the camp. • on long journeys through the arizona desert, to keep their energy and minds boosted. • during the long winter nights, when they were cold and the land was not suitable for farming.