水平仪每个微调都应轻轻转动，不要用力过大。（）不准用手触片。
A.塑料片
B.光学片
C.镜片
D.金属片
参考答案：B, C
So far, the moon is the only one of the heavenly bodies in space ______ reached by manned spaceships.
A．that has been
B．what have been
C．which has been
D．that have been
非法持有鸦片不满（）克，属于违反治安管理行为。
A.200
B.300
C.400
D.500
