— We did not see him at the lecture yesterday．
— You ______ him, since I went to an international conference with him．
A. mustn’t have seen B. can’t have seen
C. couldn’t see D. needn’t have seen
The roof began to fall ______ she had time to dash into the room to save her baby.
A. after B. as C. before D. until
Don’t be so discouraged. If you ______ such feelings, you will do better next time.
A. carry on B. get back C. break down D. put away
No such authorization ______ be given without the president’s written permission.
A．should B．shall C．would D．may
eBay sells connections，not goods，______ buyer and seller into contact with each other.
A. being put B. putting C. has put D. puts
With more forests being destroyed，huge quantities of good earth ______ each year.
A. is washing away B. is being washed away
C. are washing away D. are being washed away
