How _____ these students are listening to their teacher!

问题描述:

How _____ these students are listening to their teacher!
A.careful B.careless c.carefully D.care
我知道答案是C,为什么要选那个,我想不通,

空格里的词是修饰listening to的,也就是修饰动词的,只有副词是修饰动词的,四个选项只有C是副词,因此选C.