问题
单项选择题
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
参考答案：B
解析：
这是一个与过去事实相反的虚拟语气句，从句had they been done by hand插在主句中，采用倒装形式省略了连词if，表示非真实条件，主句中有明确的时间状语by the time they were finished，所以B选项是正确选项。
译文：所涉及的数以百万计的计算如果用手算的话，到算完时也会完全失去实际价值了。