Willingness to take turns is one way we can express our attitudes in
a. nonverbal communication.
b. written language.
c. body language.
d. spoken language.

Willingness to take turns is one wy we can express our attitude in either A or C. So either in nonverbal communication or Body language.

It's actually very hard to distinguish the two. Our willingness to take a turn can be expressed either by actual body language or simply by nonverbal communication. But you have to know that all body language by default is nonverbal communication as through it you're communicating with the other person nonverbally.