The millions of calculations involved, had they been done by hand, ______ all practical value by the time they were finished.
A. had lost B. would have lost C. would lose D. should have lost
请问：应该选什么？ had they been done by hand 是什么句式？ 整句如何翻译？ 谢谢！
The millions of calculations involved, had they been done by hand, would have lost all practical value by the time they were finished.
答案是 B。
这是2001年6月的四级考试真题。虚拟条件句，插在了句子中间，所以前后都有逗号。习惯的语序是：
If they had been done by hand, the millions of calculations involved would have lost all practical value by the time they were finished.
句子参考翻译：
所涉及的数百万次计算假如如果用手工进行，等到算完的时候可能一点儿实用价值都没了。
had they been done by hand是省if，并用倒装语序的句式。
Were it （If it were） not for their assistance, we couldn’t have got over the difficulties.
要不是他们的帮忙，大家不可能克服那些困难。
Had it not been for the reservoir, we’d never have been able to beat the drought.
要不是有这个水库，大家就不可能战胜干旱。
But that he saw it , he could not have believed it.
要不是他亲眼看见，他早就不相信了。
