在陆地勘探工作中,风化层下的()是有利的激发条件,因此往往采用井中爆炸。
A、低速层
B、降速层
C、高速层
D、岩石层
参考答案:C
In________,people in that village were very poor.
A.1920s
B.the 1920s
C.1920's
D.its 1920s