Where had it come from?它来自于哪里?我想问的是为什么come 不用过去分词?

where had it come from假如是过去完成时态的话,不应该是where had it came from Where had it come from?它来自于哪里?我想问的是为什么come 不用过去分词? The experts from the zoo were convinced that the animal was a puma,but where had it come from 为什么不用where did it come from 问 Where__it come from?各种组合的意思以下几句话：1.Where did it come from?2.Where does it come from?3.Where had it come from?4.Where is it come from?具体什么区别?什么时候用哪句话? the experts were now fully convinced that the animal was a puma,but where had it come from?As no pumas had been reported missing form any zoo in the countrybut where had it come from?这里的had为什么要用过去完成时呢 ,而且come from这 关于新概念第三册第一课有一句话一个had用法问题新概念第三册第一课后面有一句“but where had it come from”我想问一下里面的had是翻译成什么啊?可以换成was么? A. Choose the correct answer 1.Lets this play.Sorry,I like to this book. A.look, seeB.look at, read C.watch,read D.to see,look 2.Where are your socks? .A.They are on your bed.B.It's on your bed.3.Where you come fr 新概念3册第一课有点不懂的地方第二段的倒数第4行．but where had it come from?这里的come为什么不是came啊?如果是come的话不是应该是but where did it come from吗?不懂啊．． ---Bob,where were you yesterday?we had a meeting.--- ( )to come to the meeting?Nobody told me about it.A.Did I supposed B.Would I supposed C.Was I supposed D.Had I supposed 怎么填?为什么? where come where go 一首歌I know nobody know,where it come and where it goes.高手提醒下歌名 from it where come does（连词成句） THE LEGEND HAD IT THAT HAPPINESS HAS EVER COME 求翻译!the hospital where I had it done Alice left the book where she had found it. i found my unbrella where i had left it but where does it all come from?请问where后为什么有does People were disturbed and began to see where the noise ___A.is comingB.was comingC.has come D.had come