C is the obvious answer because a involves talking and b shows the same thing. D shows how people use different words which is talking. Gestures and facial expressions use hand and face, not your voice.
Nonverbal means not speaking. The answer choice must be one that does not involve words or speaking. The only option that does not have spoken words is option c. When people use gestures and facial expressions, they are adding a nonverbal layer of communication to their speech. Options A, B and D are all verbal strategies.
