345. +动词原形

344. If (we,you,he,she,it,they)+should

343. If I (we,you,he,she,it,they)+行为动词的过去式(be的过去式一般用were)通常要与一个表将来的时间的状语连用

342. 主句的动词形式

341. 条件从句的动词形式

340. ①形式：

339. ②用法：

a) I would have checked my paper again if I had had more time at yesterday’s examination.(fact:I had no more time at yesterday’s exam, so I didn’t check my paper again)

b) You would have already recovered from his illness if he had seen the doctor in good time.(fact: He didn’t see the doctor in good time ,so he hasn’t recovered from his illness )

a) 表示与将来事实相反的情况

338. 所有人称+could(might)+have+过去分词

337. they,it ) would

336. You (he,she , +have+过去分词或：