Though you have taken lots of ______,you have to do the ____on pa_英语解答

Though you have taken lots of ______,you have to do the ____on page 35.(exercise)
正确答案给的是 exercise,exercises.
请问为什么第一个不能是复数,exercise做练习讲不是可数名词吗?

人气：401 ℃　时间：2019-10-11 12:44:53

解答

第一个是锻炼、练习,是抽象名词,不可数；
第二个是练习题,具象名词,可数.