It ___ very nice if only it were possible.
A. will be
B. would be
C. is
D. were
I wish I ___ what to do.
A. knew
B. have known
C. know
D. would know
If I had hurried, I ___ the train.
A. would catch
B. could catch
C. would have caught
D. had caught
He insisted that John ___ it.
A. do
B. does
C. did
D. would do