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【单选题】
室内空气污浊时，空气离子状况发生改变，主要是A.
轻离子增多，重离子减少
B.
重离子增多，轻离子减少
C.
阴离子增多，阳离子减少
D.
阳离子增多，阴离子减少
E.
重离子、轻离子都减少
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参考解析：
知识点：
皮皮学刷刷变学霸
举一反三
【单选题】Going down a hill is like ______.
A.
falling into bad habits
B.
falling into good habits
C.
falling into water
【单选题】Why did the U.S. Navy set up underwater microphones around the world in the 160s?
A.
To listen for changes in ocean structure.
B.
To listen for changes of ocean currents or volcanic activity.
C.
To make sure whether there was a giant squid deep in the ocean.
D.
To follow the track of the Soviet warships under water.
【单选题】Why did the U.S. Navy set up underwater microphones around the world in the 1960s?
A.
To listen for changes in ocean structure.
B.
To listen for changes of ocean currents or volcanic activity.
C.
To make sure whether there was a giant squid deep in the ocean.
D.
To follow the track of the Soviet warships under water.
【简答题】任务型阅读. Lots of people like diving into water, because they can explore the underwater world. But there is another kind of diving. Some people dive into the sky! This is really a very exciting sport. ...
【简答题】The falling snow covers everything on earth. Everything on earth ______ the falling snow.
【简答题】blood-air barrier
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