II. 单项选择 (每小题1分，共15分)
( )21. My English teacher _______ the Great Wall three times since he came to China.
A. has been to B. has been C. has gone to D. has gone
( )22. Next week Li Lei is ________.
A. going a field trip B. going to a field trip
C. going on a field trip D. went on a field trip
( )23. My father likes vegetables ________ I like meat very mu ch.
A. when B. while C. before D. after
