2012大学英语四级语法：虚拟语气（一）

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表示现在/过去/将来情况的虚拟条件句  
' r3 x. w: A7 g6 _' g- y# z' }' D3 ~　　虚拟条件句主要有三种结构：
　　1)　表示与现在情况相反：主句谓语用“would / could / might +动词原形”，从句谓语用“动词的一般过去时”(动词be的过去式一律用were)。
3 J9 n' ]! j8 l% M/ d　　If I were you, I would not accept his offer.
　　If I had time, I would certainly go to the cinema with you.
& P. A8 G1 i4 q　　2) 表示与过去情况相反：主句谓语用“would / could / might + have +过去分词”，从句谓语用过去完成时。
　　If I had got up a little earlier, I wouldn’t have missed the train. 外语学习网
　　If I had been more careful, I might have passed that exam.
9 Q% b0 j2 X! E. P  O* B　　3) 表示与将来情况相反：主句谓语用“would / could / might +动词原形”，从句谓语用“were +动词不定式”或“should +动词原形”。
: g6 Y6 Z0 [# x; ?; V& }　　If I were to do the job, I would not be able to have enough time to study.
　　If it should rain tomorrow, I would not go out with you.