关于悬浮在液体中的固体微粒的布朗运动，下面说法中正确的是（ _爱下问搜题

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问题选择题

关于悬浮在液体中的固体微粒的布朗运动，下面说法中正确的是（　　）

A．微粒的无规则运动就是分子运动

B．微粒的无规则运动是微粒内部的分子运动的反映

C．微粒的无规则运动是液体分子无规则运动的反映

D．微粒运动剧烈程度只与温度有关

答案

答案：C

完形填空

Weeks passed and the ___30_____over the coming Christmas grew into restlessness until the last day of ___31___before the holiday break. I smiled in ___32____as the last of them hurried out the door. Turning around I saw David ____33___standing by my desk.
“I have something for you,” he said and ___34___ from behind his back a small box. ____35___it to me, he said anxiously. “Open it.” I took the box from him, thanked him and slowly unwrapped it. I lift the lid and to my ___36___saw nothing. I looked at David’s smiling face and back into the box and said, “The box is nice, David, but it’s ___37____”.
“Oh no, it isn’t,” said David. “It’s full of love, my mum told me before she died that love was something you couldn’t see or touch unless you know it’s there.”
Tears filled my eyes ___38___I looked at the proud dirty face that I had rarely given ____39___to. After that Christmas, David and I became good friends and I never forgot the meaning ____40___the little empty box set on my desk..

C．inaccurately

D．inappropriately

B．expectation

C．appreciation

单项选择题

在以下哪个高度以上的飞行中，服务的机组成员应接受呼吸原理、生理组织缺氧、减压的物理现象和事件等内容的教育？（）

A.20000ft

B.12000ft

C.25000ft