虚拟语气
1.比如it suggests that…sb (should) do…
在这里should可以省略,在做题时很容易错
2.与现在事实相反主句用if+did/was、were 从句用would/should/could/might+do(这里would/should/could/might)不可省略
有情态动词must,can(could),may(might),ought to,need,dare,shall(should),will(would),have(had) to,used to时后面的谓语动词用一般时