单项选择题

大气层又叫大气圈，地球就被这一层很厚的大气层包围着。下列关于大气层的说法中，正确的一项是( )。

A．大气层的厚度大约为700千米
B．云、雾、雨等现象都发生在暖层内
C．大气层的气温随高度增加而降低
D．大气层的空气密度随高度的增加而减小
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单项选择题
In the foreign trade business, the trade terms CIP is the abbreviation for ______.
A. Cost, Insurance and Freight

B. Cost and Insurance
C. Carriage and Insurance Paid to
D. Carriage Paid to
单项选择题
In case you can make a reduction ______ 5% ______ your price, we may strike the deal with you.
A．of, of
B．by, by
C．of, in
D．for , for
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