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  
; U; g) Y: B# b  @; b' d- T　　虚拟条件句主要有三种结构：
# D) n$ b. c( f. T4 A　　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)。
, m( y2 [* J+ l* O6 Y1 D' a# e& ]8 r, V　　If I were you, I would not accept his offer.
　　If I had time, I would certainly go to the cinema with you.
, s/ A! T( c' U; I　　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
# S' t3 H2 [9 _5 i: f: D　　If I had been more careful, I might have passed that exam.
/ N) j' G9 f/ m" k& @　　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”。
　　If I were to do the job, I would not be able to have enough time to study.
% `$ b' H& O8 r. s　　If it should rain tomorrow, I would not go out with you.