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【简答题】

银河系很大,一般用______作长度单位表示最方便;而分子直径很小,一般用______长度单位表示最方便.

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参考解析:
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【单选题】Isn’t it surprising that scientists have a better understanding of how many stars there are in the galaxy (银河系) than how many species there are on Earth Their estimates of global species diversity var...

A.
The soil and the deep sea belong to communities that haven’t been fully explored.
B.
It is surprising news wherever new species are discovered in the deep sea.
C.
About 90 million species are believed to live in the deep sea.
D.
A million species in the deep sea have been discovered and named.

【单选题】根据文意,天体物理学家发现的银河系“甘戈特里波”是一种()。

A.
冰川一样的结构
B.
像“羽毛”一样的气体卷须
C.
连接银河系两条旋臂的固体星系结构
D.
冷一氧化碳气体云

【单选题】纳米的长度单位是()

A.
1纳米等于千万分之一米
B.
1纳米等于亿万分之一米
C.
1纳米等于百万分之一米
D.
1纳米等]:十亿分之一米

【单选题】银河系直径()

A.
11万光年
B.
12万光年
C.
10万光年
D.
14万光年