秦始皇和汉武帝为安定北边，都曾派兵大举反击哪一游牧民族的进扰：[ ]
A．突厥
B．女真
C．契丹
D．匈奴
答案：D
成年人基础代谢水平在30岁以后每10年约降低（）
A.2%
B.4%
C.6%
D.8%
E.10%
Guangzhou was the second Chinese city to host the Asian Games because Beijing ________ the event
before.[ ]
A. had held
B. was held
C. held
D. had been held
