I knew that my turn had come.为什么用had come

I knew that my turn had come为什么用knew I knew that my turn had come. knew that my turn had come Twenty people had already left .I knew that my turn had come i knew that my turn had come.这是新概念二上面的一句话,为什么用had+动词原型这个用法? I knew that my turn had come.这句话怎样理解 I knew that my turn had come我知道这次该轮到我了!my turn是什么意识 i kenw that my turn had come为什么不用had to ? [紧急求助]I realized that she ( ) in.用had come 还是came?为什么?要如何判断? That love had come to 改成I know that my turn have come I didn't know you had come back 中的had come 不该用have came back