Though he is in his sixties, ______ he works as hard as a young man.
A. yet 　 　 　 　 B. but 　 　 　 　 C. and 　 　 　 　 D. and yet

 ___ the Internet is bringing the distance between people, it may also be breaking some homes or will cause other family problems.
   A. When              B. If               C. As               D. While

 Scientists say it may be five or ten years _____ it is possible to test this medicine on human patients.
A. since             B. before              C. after               D. when

 I had worked here ______ you came here. But I shall leave for England ______.
   A. before long, before long           B. before long; long before
   C. long before, before long           D. long before; long before

 The crowd started cheering ______ he rose to speak.                    
   A. as               B. since             C. till               D. where

--- The thread of my kite broke and it flew away.
--- I had told you it would easily break ________it was the weakest.
A. when 　 　 　 B. where 　 　 　 C. unless 　 　 　 D. since

 The roof fell _____ he had time to dash into the room to save his baby.
   A. before            B. as               C. after              D. until

 His father began to work ______ his childhood.
   A. since             B. before            C. as early as           D. while

Many places are flooded by heavy rainfalls, so they can’t walk ____they like these days.
A. when 　 　 　 　 B. whenever 　 　 C. where 　 　 　 D. wherever

 ____others say, the expert is sure that his theory is correct
   A. No matter          B. It doesn’t matter         C. Whatever         D. What