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问题 选择题

光的世界丰富多彩，光学器件在我们的生活中有广泛的应用．下列说法正确的是（　　）

A．借助放大镜看地图，地图到放大镜的距离应大于一倍焦距

B．阳光通过凸透镜可以点燃纸屑，这是由于凸透镜对光线有会聚作用

C．照相时，被照相者应站在距镜头一倍焦距和二倍焦距之间

D．人在照镜子时，总是靠近去看，因此时平面镜所成的像变大

答案

因放大镜在放大物体时，必须将物体放在一倍焦距之内，所以A是错误的；

照相时，被照相者需距镜头2倍焦距之外，所以C是错误的；

因平面镜成像时是成正立等大的虚像，人大小不变，则像大小也不变，所以D是错误的；

因凸透镜对光线有会聚作用，所以阳光通过凸透镜可以点燃纸屑，所以B是正确的．

故选B．

单项选择题

如果孔板装反了方向，那么流量指示（）

A、偏高；

B、偏低；

C、不变。
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单项选择题

Recently, I flew to Las Vegas to attend a meeting. As we were about to arrive, the pilot announced with apology that there would be a slight (16) before setting down. High desert winds had (17) the airport to close all but one runway. He said that we would be (18) the city for a few minutes waiting to (19) . We were also told to remain in our seats meanwhile with our seat belts fastened (20) there might be a few bumps(颠簸). Well, that few minutes turned into about four-five minutes, including a ride that would make a roller coaster(过山车) (21) by comparison. The movement was so fierce that several passengers felt (22) and had to use airsickness bags. As you might guess, that’ s not a good thing to have happen in a(n) (23) space because it only (24) to increase the discomfort of the situation.

About twenty minutes into the adventure, the entire airplane became very (25) There was now a sense of anxiety and fear that could be (26) noticed. Every passenger simply held on for dear life …except one. A (27) was having a good time！ With each bump of the (28) , he would let out a giggle (咯咯地笑)of delight. As I observed this, I (29) that he didn’t know he was supposed to be afraid and worried about his (30) . He neither thought about the past nor about the future. Those are what we gown--ups have learned from (31) . He was (32) the ride because he had not yet been taught to fear it. Having understood this, I took a deep breath and (33) back into my seat, pretending I was (34) on a roller coaster. I smiled for the rest of the flight. I even (35) to giggle once or twice, much to the chagrin(随恼) of the man sitting next to me holding the airsickness bag.

（30）（）

A．health

B．safety

C．joy

D．future
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