（）是人民防空的重点。
A.城市
B.群众
C.政府
D.农村
参考答案：A
声音在空气中传播的速度为______米/秒；雨夜，一闪电过后3秒才传来雷声，声音隆隆持续2秒才停止，放电的地方与你的距离是______米．
_______by the rising price of gas, many car owners use their cars less frequently. [ ]
A. Driven
B. Being driven
C. To drive
D. Having driven
