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问题 单项选择题

APU连续起动限制是（）

A、可连续起动三次，每次之间无时间限制

B、可连续起动三次，但第二次与第三次之间应等待15分钟

C、可连续起动三次，每次之间应等待5分钟

D、无次数限制，但每次之间必须有足够的冷却时间

答案

参考答案：B

完形填空

Light and shadow (影子) are friends. They usually go together. We receive light every day. __________小题1:________________

Light cannot shine through you. ___________小题2:________________ There is a spot(斑点) on the ground next to you. The light cannot reach the dark spot. This is your shadow. 

______________小题3:_____________Your body stops very little light from reaching the ground. So your shadow is quite short.  

But in early morning or late afternoon the sun is low in the sky. The light moves over more of your body. ___________小题4:_________________ Your body keeps a lot of light from reaching the ground. 

We love light, especially sunlight. _____________小题5:______________Most of us like to stand in the shadow of a tree in summer. But some people are afraid of their own shadow at night. They do not want to walk in a dark street. They do not want to see the shadow, either. But still light and shadow usually go together.

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填空题

站内正线轨道电路移频化，一般采用（）的方式。
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