机器与机构的相同点在于()。 A.能够实现其它形式能量和机械能的转换 B.各个组成部

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问题:

机器与机构的相同点在于()。

A.能够实现其它形式能量和机械能的转换

B.各个组成部分之间具有确定的相对运动

C.能够实现运动和动力的传递

D.是一种人为的实物组合

E.代替人的劳动去做有用的机械功

考点:资产评估师机电设备评估基础综合练习机电设备评估基础综合练习题库
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0.0000426用科学记数法表示(保留两个有效数字)为______.

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19世纪著名的进化论的建立者___________,在仔细比较了人和现代类人猿的相似处之后,提出了人类和类人猿的共同祖先是_____________。

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                                       D

You may picture firefighters holding a hose (水管) outside of a burning building, but the Golden Eagles Hotshots don’t fight fires quite that way. When they go into action, you may not even see a fire truck.

The Hotshots are firefighters who battle fires in wildness areas. But don’t think you’ll only find them in their home state California. Wherever there is a national wildfire emergency, the Golden Eagles Hotshots could be there.

But these firefighters don’t work the same way as firefighters in a big city. They work in areas where there are a large number of trees, bushes, and grass. They climb up and down steep hills to clear brush and burnable debris(残骸). They sometimes use water, but they often fight fire with fire!

They do that by lighting what are called “backfires,” which are small, controlled fires that burn up fuel in the path of large wildfires. That way, when the wildfire gets there, it has nothing to burn and nowhere to go, because all the burnable fuel has already gone up in smoke.

The Hotshots also clear away fuel using old-fashioned hard work. For example, they use a saw to cut away trees and heavy brush that could catch fire.

Of course there are times when the Golden Eagles Hotshots do have trucks to supply water to the fires. But the water is limited, and these guys have to rely on hard work more than anything. Physical fitness is very important. They have to be in great physical shape to handle steep hills and difficult terrain(地形) while carrying a 60-pound pack.

The Golden Eagles Hotshots definitely work hard for their pay. But thanks to their efforts, many lives have been saved, many houses have not burned, and countless trees are still standing.

小题1:67. The firefighters mentioned in the passenger. 

A.do much of their work in California

B.avoid climbing steep hills in their work

C.do their work equipped with advanced tools.

D.carry out their work mostly in forests and mountains.小题2:68. According to the passage, why do the firefighters light “backfires”?

A.To signal for help.

B.To remove obstacles.

C.To protect trees and bushes.

D.To prevent the fire from spreading.小题3:69. What can we learn about the Golden Eagles Hotshots?

A.They are firefighters working in big cities.

B.Their work requires physical strength.

C.They are voluntary firefighters working for free.

D.They usually hold a hose to put out the fires.小题4:70. What is the author’s attitude towards the Golden Eagles Hotshots?

A.Appreciative

B.Doubtful

C.Worried

D.Critical

题型:多项选择题

关于螺杆泵不正确的说法是()。

A.切断电源而泵未完全停转时,不宜先关吸入阀

B.可以关吸、排阀并松调压阀,卸压启动

C.长时间小流量工作,应将旁通调压阀调松

D.初次使用或拆修后装复使用前应向泵内灌油

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张家山汉简

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