在主句为一般过去时的句子中 as though 引导的状语从句假如用虚拟语气谓语可以不是 have done 而是 did 吗?
But what else could they do on that dark winter's day when the last oftheir store of grain was gone, when the trees were cut and sold, when he hadsold everything, even the little they had saved from the flood, and there wasnothing left except the rafters of the house they had and the garments theywore? Was there sense in stripping the coat off one's back to feed one's belly?Besides, the beast was starving also, since the water had covered even thegrass lands, and they had had to go far afield to gather even enough to cookits bones and flesh. On that day when he had seen the faces of his old parentsset as though dead, on that day when he had heard the crying of his childrenand seen his little daughter dying, such a despair had seized him as made him likea man without his reason, so that he had gathered together his feeble strengthand he had done what he said he never would; he had taken the kitchen knife andgone out and killed his own beast. When he did it, even in his despair, hegroaned, for it was as though he killedhis own brother. To him it was the last sacrifice.
（源于赛珍珠《贫瘠的春季》）
请问老师这一段落中的 killed 为何不是 have killed 呢？回忆所学内容，主句为一般过去时的时候，as though 引导的状语从句倘若不符合事实，后面的谓语动词应该为 have killed ，但文段里面不是。这是为何呢？如此的句子符合语法吗，还是某种特殊使用方法？请老师指教。
整个段落都是过去式，如何能蹦出来个目前完成时 have killed 呢？即便用虚拟，也应该是had killed。所以这里不是虚拟语气，尽管不是事实，as though/if后也可以用陈述语气。具体你可以查语法书。
