A computer____think for itself ; it must be told what to do.(b)

问题描述:

A computer____think for itself ; it must be told what to do.(b)
A.can’t B.couldn’t C.may not D.might not
我觉得A也可以

我也这样认为 AB语法上都讲得通
对中取优 couldn't比can't委婉 一般题中有couldn't都选它,除非题目中有“不可能”(can't have done)之意出现时才用can't