careful与carefully的用法

简单说来,因为句子中用的是be动词,be动词后跟形容词, 动词后跟副词在这里句中用的be动词“are”,所以后面跟形容词careful enough如果要用carefully enough的话,这句话要改写成 None of the students can work carefully enough on the math problem 之类。