虚拟 （基本不考，不重要）
虚拟就是通过谓语动词的变态表示非真实。虚拟分时态还分主/从句虚拟可以用于很多句式中，常用的是下面两种句式：
1. if 条件句的虚拟
变态方式: 从句往前推，主句4+1，将来同现在
- 假设现在
if 从句要从现在时往前推一个时态变成一般过去时 did，如果是 be 动词要用 were，主句要用 4 种情态动词 cound/would/should/might + do
If I had a billion dollars, I would donate all the money to the charity.
- 假设过去
if 从句要从过去时往前推一个时态变成过去完成时 had done，如果是 be 动词要用 were，主句要用 4 种情态动词 cound/would/should/might + have done
If he had played last season, we would have won the match.
- 假设将来 (用的最少)
if 从句要从现在时往前推一个时态变成一般过去时 did，如果是 be 动词要用 were，
或者用 were to do 和 should do (可以不记，那就和假设现在用法一致)，主句要用 4 种情态动词 cound/would/should/might + do
If I were to live my life over again, I would have you as my life.
If I lived my life over again, I would have you as my life.
If I should live my life over again, I would have you as my life.
2. 宾语(动宾)从句的虚拟
当主句中的谓语动词表示 "建议、命令、要求" 时，后面的宾语从句才需要使用虚拟。从句的谓语动词用 should + 动词原型， should 可以省略。
建议： suggest / advise / propose / recommend ...
命令： order ...
要求： ask / demand / insist / requir / request ...
He ordered they (should) start the attack before dawn.
The workers demended they (should) be given the wages they should get.
