内装电动机主轴传动结构有效地提高了主轴部件的（）。 A.韧性 B.刚度 C.强度 D

You cannot see any object unless light from that object gets into your eyes. Some of the things you see give off light of their own. The sun, the stars, a lighted lamp are examples that can be ssen by their own light. Such things are luminous. Most of the things you see are not giving off light of their own. They are simply reflecting light that falls on them from the sun or some other luminous bodies. Then moon , for example , does not give off any light of its own. It is non-luminous. You see it because sunlight falls on it and some of it reflects in your direction. So moonlight is only secondhand sunlight.

When you look at a book, it sends your eyes some of the light that falls on it, and you see the book. If light could be kept out from where you are so that there would be no light for the book to reflect, then you could not see the book even with your eyes wide open.

Light travels so fast that the time in which it travels from the book you are reading to your eyes is so short as if it took no time at all. Light reaches us form the moon , which is about 380,000 kilometers away, in only a little more than a second.

小题1:You can see the book because___________.

A．your eyes are close to it .

B．it reflects light

C．it has light of its own

D．your eyes can get to it小题2:The word “ reflects”  means____________.

A．throws back

B．takes back

C．gives off

D．sends out小题3:    ___________ have light of their won.

A．the sun and the moon

B．The stars and the earth

C．The sun and the stars

D．The moon and the earth

X与Y两元素的阳离子具有相同的电子层结构，X元素的阳离子半径大于Y 元素的阳离子半径，Y与Z两元素的核外电子层数相同，Z元素的第一电离能大于Y元素的第一电离能，则X、Y、Z的原子序数的顺序为 [ ]

A.X>Y>Z

B.Y>X>Z

C.Z>X>Y

D.Z>Y>X

对投资项目决策分析与评价而言意味着提出推迟或否决项目的建议是风险对策中( )的体现。

A．风险回避

B．风险控制

C．风险转移

D．风险自担

教师的教育能力主要表现在哪些方面？

《中华人民共和国农业机械化促进法》规定，（）应当依法加强对农业机械产品市场的监督管理工作。

A.产品质量监督部门

B.工商行政管理部门

C.国务院农业行政主管部门

D.省级人民政府主管农业机械化工作的部门