1.Because of the rain,we____do morning exercises.
A.needn't to B.mustn't C.don't need to D.need to
2.My mother was tired last night,so I___for her.
A.ate up B.washed up C.cleaned over D.washed over
3.He didn't study hard.As a result,he_____(not pass)the dinal exam.
4.Scientists__have developed__(develop)different kinds of robots in the past few years.