Question

Shall we go to see a movie tonight ? _____let's go. A,Why not ? B.Ok! 为何选A？

Answer 1

I think A, C and D are all correct, and even B might be correct except that it sounds pretty awkward for a native speaker.

Shall we go to a movie tonight?
A. Why not?
C. Certainly.
D. Ok.

Frankly, of these three correct answers, I find "Ok" to be the weakest. If someone said "Ok" to me in these circumstances, I would think that maybe they were just agreeing in order to be polite, and maybe didn't really want to go.

Answer 2

这是一般的日常用语，和文化有关，
一般中国人喜欢说：好啊！但是英语中一般都用：why not？表示赞同

Answer 3

why not表示为什么不? 前面一句是询问说我们今晚去看电影，所以回答选择why not.

Answer 4

每个国家对 每句话有不同的说法

Answer 5

为什么不？其实是表示赞同。