. The millions of calculations involved,_爱下问搜题

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问题选择题

. The millions of calculations involved, had they been done by hand, _____ all practical value by the time they were finished.

A．could lose

B．would have lost

C．might lose

D．ought to have lost

答案

答案：B

选择题

设a，b是向量，命题“若a≠-b，则|a|=|b|”的逆命题是[ ]

A.若a≠-b，则|a|≠|b|

B.若a=-b，则|a|≠|b|

C.|a|≠|b|，则a≠-b

D.若|a|=|b|，则a≠-b

单项选择题

下列哪项属于静脉肾盂造影的禁忌证()

A．肾盂结石

B．膀胱结石

C． * * 狭窄

D．肾动脉狭窄

E．严重血尿