岩屑下沉速度在紊流中比在层流中（）。
A、小
B、一样
C、大
D、都不对
参考答案：C
Things made by hand are usually more expensive than _________ produced in factories.
A．these
B．this
C．that
D．those
为什么说五四运动是中国新民主主义革命的开端？
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