We __________ our lives had it not been for the policeman.

A. would have lost     B. should lose       C. might lose        D. could have lost

If we throw away too much waste and can’t keep good ecosystem,we _________ our future.

A.must have destroyed          B.could be destroying ?

C.may be destroying             D.must destroy ?

---When shall we restart our business?

   --- Not until we       our plan.

   A. will finish  B. are finishing C. are to finish      D. have finished

— When shall we restart our business？
— Not until we       our plan．

We______our breakfast when an old man came to the door.

A.just have had             B.have just had             C.just had                     D.had just had