单选题 The millions of calculations involved, ______ by hand, would have lost all practical value by the time they were finished.
  • [A] bad they been done
  • [B] they had been done
  • [C] having been done
  • [D] they were done


【正确答案】 A
【答案解析】虚拟语气题。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。