选B为什么不行？

_____,I'd have told you.

虚拟语气 与现在相反 从句IF + 主语+动词过去式 主句 主语+WOULD/SHOULD+ 动词原形 与过去相反 从句 IF+主语+动词的过去完成式 主句 主语+SHOULD+HAVE+过去分词 与将来相反 从句A 谓语用动词典过去式 B谓语用WERE TO +动词原形 C谓语用SHOULD+动词原形 主句 主语+/WOULD/SHOULD+动词原形 从句如省略IF，用倒装句式“WERE/HAD/SHOULD+主语 eg。 Were I in school again ,I would work harder。 与现在事实相反 原句 If I were i...全部

  虚拟语气 与现在相反 从句IF + 主语+动词过去式 主句 主语+WOULD/SHOULD+ 动词原形 与过去相反 从句 IF+主语+动词的过去完成式 主句 主语+SHOULD+HAVE+过去分词 与将来相反 从句A 谓语用动词典过去式 B谓语用WERE TO +动词原形 C谓语用SHOULD+动词原形 主句 主语+/WOULD/SHOULD+动词原形 从句如省略IF，用倒装句式“WERE/HAD/SHOULD+主语 eg。
   Were I in school again ,I would work harder。 与现在事实相反 原句 If I were in school… Had you been here earlier,you would have seen him。
   与过去事实相反 原句 If you had been here… Should there be a meeting tomorrow,I would come。 与将来相反 原句If there should be a meeting… 题目中这句话是对过去事实的相反，如果我已经知道了，就告诉你了 If I had known it,I would have told you。
   省略IF，所以选C 。收起