A.I have not been to the museum for a year.
B.A year ago, I often went to the museum.
C.My going to the museum lasted a year.
D.At last I went to the museum after a year.

A.to be asking
B.to be asked
C.being asking
D.of asking

A.is going to be performed
B.has been performed
C.will be performing
D.will have performed

A.had left / forgot
B.was leaving / was forgetting
C.left / had forgot
D.had been leaving / would forget

A.was trying / slipped / fell
B.tried / was slipping / falling
C.had been trying / slipped/ was falling
D.has tried / slips / falls

A.see / am walking
B.saw / was walking
C.was seeing / walked
D.have seen / were walking

A.wouldn’t
B.oughtn’t
C.needn’t
D.couldn’t

A.lost / have left
B.have lost / leave
C.have lost / left
D.were losing / had left

A.have gone / did not pay
B.will go / did not paid
C.go / would not pay
D.went / had not paid

A.does not rain
B.has not rained
C.had not rained
D.would not rain