1.  __________, I would not have made such a serious mistake.

           A. If I were more careful                      B. Were I more careful

           C. Had I been more careful                     D. If I have been more careful

2.  ______ there be a flood, what ________?

           A. Had ... would we have done                  B. Should ... should we do

           C. Should ... we would do                     D. Would ... would we do

3.  All of us have been waiting for you. You _______ your promise to be here on time.

           A. ought to keep         B. might have kept        C. must have kept     D. should have kept