I believe it would be
D. Facial Expressions
my reason for this statement is because in both a performed version of a speech and written version. You practice the expression because you wish to get the listener involved into the topic you are discussing. Whereas in a written speech you facial expressions happen automatically, based on the topic and how much you understand.
I'm not sure if this is 100% right, or not. I would appreciate it if you could let me know if I was right or if my answer was way off. I'll try to do a little bit more research on it for you if you'd like.
