yes,i do用法

Question

Yes,I do 的用法
You're going to publish my book.Are you serious?
_____.It's to be published nest month.
C.Yes,I do
D.Yes,I have never been more serious
我知道D肯定是对的,但是C为什么不行呢?
应该也可以表示肯定的意思吧?

Answer 1

这里不能用 I do 来回答的 ,问句中并没有出现助动词,所以,如果要回答的话,应该是Yes,I am.