The millions of calculations involved,_____by hand, would have lost all practica

游客2023-11-05 62

问题 The millions of calculations involved,_____by hand, would have lost all practical value by the time they were finished.

选项 A、had they been done
B、they had been done
C、having been done
D、they were done

答案 A

解析这是一句虚拟语气的句子，条件句使用了省略if的倒装句形式，动作与过去事实相反。

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