( )Mary and her classmates that helped the old man clean his house

问题描述:

( )Mary and her classmates that helped the old man clean his house
A.it were B.they were C.it was D.there were

选C
句型:it is s.b /s.th that.
此类句型不管it 后面跟的是单数或是复数,均视作一个单的物品,所以用单数,判断选C