月球的哪部分发现了水冰()A、内部B、表面C、北极D、南极

题型:单项选择题

问题:

月球的哪部分发现了水冰()

A、内部

B、表面

C、北极

D、南极

考点:天文学天文学题库
题型:单项选择题

下列关于用高倍镜观察人的口腔上皮细胞线粒体实验的说法,不正确的是[ ]

A.牙签消毒、实验前漱口都是为了保证实验的准确性

B.制装片时在载玻片上滴一滴0.9%的NaCl溶液,目的是维持口腔上皮细胞的正常形态

C.在高倍镜下观察可以看到活细胞的线粒体呈蓝绿色,而细胞质接近无色

D.高倍镜下观察可以看到线粒体有两层膜

题型:单项选择题

III. 完形填空(Cloze)(共15小题;每小题1分,计15分)

A) 阅读下面的短文,结合文意用右边所给单词的适当形式填空。(For questions 66—70, read the passage below. Use the word given in bold at the end of the line to form a word that fits in the space in the same line.)

Sharon Sexton

She throws Sean Penn over her shoulder and she asked Andrew Ridgeley to be quiet. She's slim, (66) ________ 【attract】and 1.75 meters tall. Sharon Sexton is not what most of us (67) ________ 【image】a bouncer (保镖) to look like but that's just what she is at the London club, Xenon.

Sharon says: “The aim is not to be noticed. I have to move around and mix in with the crowds. I'm here to make sure no trouble starts. If anyone looks (68) ________ 【anger】I just go and ask them to keep calm. Most men are so surprised at being spoken to by a woman bouncer that they don't argue. I only very (69) ________ 【occasion】have to use force.”

Sharon has also worked as a (70) “________”【mind】 for  Madonna and for Al Pacino. She spends a lot time practicing Wing Chun, a method of self-defense designed for women.

题型:单项选择题

如图所示,粗糙长木板l的一端固定在铰链上,木块放在木板上,开始木板处于水平位置.当木板向下转动,θ角逐渐增大的过程中,摩擦力Ff的大小随θ角变化最有可能的是选项图中的(  )

A.

B.

C.

D.

题型:单项选择题

卧式车床进给传动系统中,为何既有光杠又有丝杠来实现刀架的直线运动? 可否单独设置丝杠或光杠?为什么?

题型:单项选择题

制动初速度为350km/h时,列车紧急制动距离限值为()m。

A、6000

B、6500

C、6800

D、7000

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