A ,time时间 ,不可数名词.排除CD,修饰名词用What.
what + a/an + 形容词+名词（单数）+ （主语+ 谓语）
例如：What a good book it is!
What an interesting film it is!
what + 形容词 + 名词（可数复数、不可数）
What fine days!
What fine weather it is!
how + 形容词（副词）+ 主语 + 谓语
How fine it is today!
How hard he studies!