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参考答案：
参考解析：
刷刷题刷刷变学霸
举一反三
【单选题】对于地球同步卫星的认识，正确的是 [ ]
A.
它们只能在赤道的正上方，但为避免通行卫星在轨道上相撞，应使它们运行在半径不同的轨道上
B.
它们运行的角速度与地球自转角速度相同，相对地球静止
C.
不同卫星的轨道半径都相同，且一定在赤道的正上方，它们以第一宇宙速度运行
D.
它们可在我国北京上空运行，故用于我国的电视广播
【单选题】Passage 18 We all know that it is possible for ordinary people to make their homes on the equator (赤道), although often they may feel uncomfortably hot there. Millions do it. But as for t...
A.
in warm air
B.
in cold air
C.
when it reaches the polar region
D.
only when the clouds are down low
【单选题】Mars Global Surveyor is the oldest of five NASA robotic devices, which is designed to find out signs that Mars once had water;and it had been taking detailed pictures of the red planet for a decade. U...
A.
its life
B.
its orbit
C.
its power
D.
its position
【单选题】Kenya Wildlife Safari from ￡995DAY 1 LONDON/NAIROBIDaylight flight to Nairobi．On arrival, check in at the Holiday Inn Mayfair Court.DAY 2-4 SAMBURU AND TREETOPSSet off on safari, driving north, to the...
A.
traveling long distance
B.
spending nights outdoors
C.
watching animals in the wild
D.
seeing different kinds of plants