21. George. W. Bush, _______ President of the United States, is to visit China _______ third time.
A. a；a B. the；a C. /；a D. /；the
22. After the heavy rain, the level of the lake rose ___ 1 meter ___ 8 meters.
A. to; by B. by; to C. of; to D. to; to
23. The meetings are very short, so there is little _____ to have a real discussion.
A. challenge B. change C. chance D. chapter
