she can't have written to me , or --- the letter by now

他不可能给我写信了.can't have done 不可能,表示对过去的猜测.
or I'd have got the letter by now.= or I would have got the letter by now
否则的话,我现在已经收到信了.
否则的话,也就是 如果她给我写了信的话.
这里是与过去 事实相反的虚拟条件句,If sb.had done...,sb.would have done...
所以C答案正确.
再问： can't和 by now 不应该是与现在相反吗 谢谢
再答： by now适合的时态是现在完成时， 动作发生在过去。