Time waits for no man． But some people won't realize the importance of time______it's gone．（ ）
A．asB．sinceC．whenD．until
nice weather today!Let's go hiking．（ ）
A．HowB．What aC．What
Sixteen﹣year﹣olds should not to drive．（ ）
A．allowingB．be allowedC．allow
May I speak to Mr．Smith？
Sorry，he isn't in．He Changsha．（ ）
A．has been toB．has gone to
C．went to
During the May Day holiday， visitors came to Zhijiang to visit the Memorial Hall of Flying Tigers．（ ）
A．thousand ofB．thousands
C．thousands of
Which city is beautiful，Hangzhou，Beijing or Shanghai？
Hangzhou，I think．（ ）
A．the mostB．the betterC．more