高中英语改错Some Americans judge success on the length 76． of his

高中英语改错
Some Americans judge success on the length 76．
of his vacations .The man who gets a month’s 77．
vacation each year consider himself more successful 78．
than the man gets two weeks .Many people want 79．
to be teachers because it is teachers who can 80．
get a three-month vacation every year .Some college 81．
teachers who teach the three classes consider 82．
themselves less successful than that who teach 83．
only one or two ,or none in all .In short ,the less 84．
work Americans do ,the less successful they 85．
consider themselves .
第79句Many people want to be teachers because it is teachers who can get a three-month vacation every year 正确答案并没有错误,这句话我不是很明白 it is teachers who can get a three-month vacation,为什么用it is teachers?为什么teacher是复数?it is 不是应该+单数名词吗?