频率为100Hz的声音 [ ]
A.每分钟振动100次
B.人耳听不见
C.响度比10Hz的一定大
D.以上都不对
答案：D
堆肥、人粪尿与过磷酸钙的混合情况为（）。
A.宜于混合
B.可以暂时混合
C.不宜混合
The foreign guests said that they were very happy （）the great changes which had taken place in the village.
A.to
B.for
C.about
D.by
