设河水对船的阻力与船的速度大小成正比，起初船以较低速度匀速行_爱下问搜题

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问题不定项选择

设河水对船的阻力与船的速度大小成正比，起初船以较低速度匀速行驶，那么当船加倍匀速行驶时，轮船发动机的功率是原来的[ ]

A．2倍

B．4倍

C．倍

D．倍

答案

B

选择题

After ________ half a kilometer, I ________ feel tired. [ ]

A. run, begin to

B. running, began to

C. to run, began to

D. running, begin with

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