History tells us that in ancient Babylon, the cradle of civilization, the people tried to build a tower that would reach heaven.

A．center of civilization

B．place where civilization started

C．place where civilization was yet to emerge

D．the earliest period of civilization

根据（）的不同特征又可以将对流层分为行星边界层或摩擦层和自由大气。

A．气温

B．大气运动

C．湿度

D．气压