If it had been fine yesterday,we could have watched that air

If it had been fine yesterday,we could have watched that air show.,这一句话是虚拟语气.意思是,如果昨天是晴天,我们就可以看空中表演了.潜意思就是,昨天并不是晴天,而是雨天.has rained的意思是过去下雨,一直下到现在.句子中并没有这个意思,也没有跟其他时间做比较.所以用rained就好.
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