Were they here now, they could help us.

Had you come earlier, you would have met him

注意：

在虚拟语气的从句中，动词'be'的形式一律用"were"，不用was。 特殊的虚拟语气词：should

1） It is demanded / necessary / a pity + that …(should) +动词原形 It is suggested that we (should) hold a meeting next week. It is necessary that he (should) come to our meeting tomorrow.

2）在宾语从句中的应用

在表示命令、建议、要求等一类动词后面的从句中。

order, suggest, propose, require, demand, request, insist, command, insist +that (should) do

I suggest that we (should) hold a meeting next week.

3）在表语从句，同位语从句中的应用

在suggestion, proposal, idea, plan, order, advice等名词后面的表语从句、同位语从句中要用虚拟语气，即（should）+动词原形。