每次放水量的大小,取决于放水器的()。
A、容积
B、容积、抽放负压
C、抽放负压
参考答案:B
What will the speaker probably talk about next().
A.Cases of physical or sexual abuse.
B.Types of abusive parents.
C.Consequences of child abuse.
D.Laws against child abuse.
如图所示,扇形A0B为透明柱状介质的横截面,半径为R,介质折射率为3,圆心角∠A0B=30°,一束平行于OB的单色光由OA面射入介质.要使柱体AB面没有光线射出,至少要在O点竖直放置多高的遮光板?