英语语法分析,虚拟语气Themillionsofcalculationsinvolved,hadtheybeendonebyhand,allpracticalvaluewouldhavelostbythetimetheywerefinished.为什么这句话是虚拟语气,为什么hadtheybeendonebyhand要倒装

Question

英语语法分析,虚拟语气
The millions of calculations involved, had they been done by hand, all practical value would have lost by the time they were finished.
为什么这句话是虚拟语气,为什么had they been done by hand 要倒装

Answer 1

(If )they had been done by hand 省略了If作状语