题目: 如图是演示微小形变的装置,图中A为激光笔,B、C是两块平面镜,重物M放到桌面P上,当将重物拿走后光斑将( )A.由D向D′移B.由D′向D移C.不移动D.不能确定 答案: B镜子上放重物M后,镜子受到弹力作用而向下凹,根据镜面反射的特点知反射的光线偏向右方,当将重物拿走后弹力消失,光斑将由D′向D移,B正确.故选B
题型:选择题 The university estimates that living expenses for international students________around $8,450 a year,which________a burden for some of them. (2013·湖南,33)A.are;isB.are;areC.is;areD.is;is 查看答案