Not until all the fish died in the river        how serious the problem of water pollution was.

       A．did they realize       B．they did realize C．had they realized     D．they had realized

_______, I’d have told you.

A.  If I would have known         B.  If I had have known

C.  Had I known                   D.  Should I know

_______ towards the suffering people that they made a trip to Yushu to help the trapped.
A. So selfless and warmhearted the young couple were    
B. So selfless and warmhearted were the young couple
C. How selfless and warmhearted the young couple were 
D. The young couple were such selfless and warmhearted

_______ she was your friend, I would have invited her to the party.

  A. If I know           B. Were I to know       C. If I knew          D. Had I known

By no means _______ say like that. It is likely to spoil your relationship.

A. ought you     B. you ought to      C. should you    D. you should to

I was told that by 1990 things were beginning to improve, _________ quickly enough.
A. even if not B. even I didn’t improve

C. if not improved  D. if even to improve not

______ hard before, he failed in the exam.

A. Never have worked                                B. Never worked  

C. Having never worked　　                 D. Never having worked

Only when you ______ what you have learned to practise ______ say you have made it.

A．adapt; you can     B．apply; can you     C．use; you can     D．adopt; can you

Little ________ about his own safety, though he was in great danger himself.
A. does he care    B. did he care    C. he cares    D. he cared

________ as he was, he looked quite calm in that difficult situation.

A. A child    B. The child    C. Children    D. Child