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问题 单项选择题

110kV及以上的配电装置，一般将避雷针装在配电装置的架构或房顶上，但在电阻率大于( )地区，宜装设独立避雷针。

A．350Ω·m；
B．500Ω·m；
C．750Ω·m；
D．1000Ω·m。

答案

参考答案：D

选择题

肩负我国首次太空行走运载任务的神舟七号飞船，在绕地球五圈后成功地由椭圆轨道变成圆形轨道，在圆形轨道上飞船离地面的距离约为350km，绕行周期约为90min。设飞船在圆形轨道上的运动为匀速圆周运动，已知第一宇宙速度为7.9km/s，下述说法正确的是

A．飞船的轨道平面一定是垂直于地球自转轴的圆面

B．飞船在圆形轨道上运动的线速度大小一定大于7.9km／s

C．飞船离开地面时的发射速度一定大于7.9km／s

D．对于飞船来说，它离地面越高，其绕行速度一定越大
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单项选择题

Questions 81-90 are based on the following passage.


It sounds like a science fiction, but researchers say it’s a scientific fact: Microscopic organisms dubbed "killer algae" are paralyzing fish with unknown toxins and then eating away at their flesh. They might be making people sick, too.
The name given to this single-cell organism, or dinoflagellate, is Pfiesteria piscimorte- literally, "fish killer. " It was discovered at North Carolina State University in 1988, but at the same time, few scientists believed in its existence, much less in its highly unusual predatory nature. But ongoing research has led to international acknowledgment of the phenomenon and, recently, research funding.
Seemingly prompted by an unknown substance secreted by fish, the aggressive creature swims into action. It sends neurotoxins into the water and air, paralyzing a fish’s nervous system, and causing it to gasp for air at the surface. Eventually the fish suffocates. The killer dinoflagellate then attaches itself to the fish and begins sucking away at its flesh. This macabre scenario may help solve several sea mysteries, such as why fishermen report seeing "fish walks" (fish trying to leave the water) and pools of dead fish with holes eaten through them.
Whether humans are affected by the dinoflagellate’s toxin remains to be seen. Researchers think it’s unlikely eating fresh fish are in danger, but anyone with frequent exposure to the creature could be in peril. Several researchers working with the algae have reported bouts of memory loss and disorientation.
To understand the killer algae further, scientists must fully characterize their toxin and determine what stimulates them to attack. They also need to know if the algae are hurting fish populations, and whether pollutants make them more likely to attack.

The word "literally" underlined in Paragraph 2 most probably means ______.

A. namely
B. superficially
C. imaginatively
D. actually
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