你好，以下是我的看法1.B since引导一个时间状语从句，since后要用时间点，过去式came。关于过去完成时的用法，试着比较这两句话：Tom said that it was over ten years since he came to live in Beijing.Tom said that he had lived in Shanghai for 13 years before he came to live in Beijing.也就是说，只有主句才会用到过去完成时态（过去分词），从句只是一个时间点，用过去式。或者当主句用现在完成时态时，从句用一般现在时态的动词。2.可以用虚拟语气
