七、动词虚拟语气中条件从句与主句库存语的变化形式表（分别以 be 和 do 为例）

主从句动词变化

时间概念

从 句

主 句

与现在事实相反

were

would （ should ， could ， might ） be

did

would （ should ， could ， might ） do

与过去事实相反

had been

would （ should ， could ， might ） have been

had done

would （ should ， culd ， might ） have done

与将来事实可能相反

should be/were

would （ should ， could ， might ） be

should to/did/were to do

would （ should ， could ， might ） do

注：①此表不含混合虚拟条件句和含蓄虚拟条件句；

②此表不含主语、宾语、定语和状语从句中出现的虚拟语气；

③倒装虚拟条件句的表示：将条件从句谓语中的连系动词 were 或助动词 had 或 should 置于主语之前，把 if 省略。例如：

  1. Were they here now（=if they were thre now）， theycould help us．

  2. Had you come earlier（＝if you had come earlier），youshould have met him．

  3. Should it rain（＝If it should rain）， the crops wouldbe saved．