问题
选择题
飞机着陆后还要在跑道上滑行一段距离，机舱内的乘客透过窗户看到树木向后移动，乘客选择的参考系是（ ）
A．停在机场的飞机
B．候机大楼
C．乘客乘坐的飞机
D．飞机跑道
答案
乘客随飞机相对地面向前运动，故路旁的树木相对于飞机向后运动，所以当乘客透过窗户看到跑道旁的树木以一定的速度向后退时，该乘客选择的参考系是自己乘坐的飞机．故C正确．
故选C．
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飞机着陆后还要在跑道上滑行一段距离，机舱内的乘客透过窗户看到树木向后移动，乘客选择的参考系是（ ）
A．停在机场的飞机
B．候机大楼
C．乘客乘坐的飞机
D．飞机跑道
乘客随飞机相对地面向前运动，故路旁的树木相对于飞机向后运动，所以当乘客透过窗户看到跑道旁的树木以一定的速度向后退时，该乘客选择的参考系是自己乘坐的飞机．故C正确．
故选C．
Our eyes are very important. But many of us pay little attention to the importance of eye care. It is said that if you take care of your body, then you can surely be healthy. That is why our eyes should be given a lot of care. 小题1: . There are several causes leading to your poor eyesight. Like Televisions, computers and reading. Something dirty can cause redness (红肿) and they will make you feel uncomfortable. If this happens, the best way is to clean your eyes by using cold water. 小题2: . For example, wearing sunglasses can serve as a great way to protect your eyesight from UV rays (紫外线) in the strong sunlight. Some foods will do good to your eyesight. Remember that vitamins A, C and E are good for eyes. Try to eat food groups that have these vitamins. 小题3: . If a person exercises regularly and eats the right kind of food, his eyes will stay in good condition for a long time. All above are natural ways of eye care that help us keep healthy eyes. 小题4: . In a word, eye care is very important, no matter how old a person is. 
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