阎锡山的军事力量主要集中在中国哪一个省份？（）
A.湖南
B.福建
C.山西
D.新疆
参考答案：C
Only when _____ to explain ____ the reason for this. [ ]
A. did he start; she realized
B. he started; did she realize
C. did he start; she had realized
D. he started; had she realized
要城市或工矿区，观测场应选择在（）.
A.城市或工矿区最多风向的上风方
B.城市或工矿区最多风向的下风方
