You can't be image_________ great fun chatting online is.答案是what ,请问为什么不能用how great fun?

问题描述:

You can't be image_________ great fun chatting online is.
答案是what ,请问为什么不能用how great fun?

感叹句中如果名词是不可数名词或者可数名词复数,必须用what!