我在学特殊疑问词的时候，老师之前讲过要把助动词或者原句中有的助动词或者Be动词放到疑问词的后面，然后剩下的那个动词要保持原型，比如：He bought tree books yesterday,变成疑问句后成了：what did he buy yesterday.可是下面这个句子，为什么动词没有变成原型呢？how long have they been in china?还有how long have they learned chinese?里面还是Been和learned
He bought tree books yesterday.变成疑问句后成了：What did he buy yesterday.是因为这是一般过去时态，需要借助助动词did来帮助提问，因为过去式形式转移到助动词do身上了，所以动词就还原了。 而how long have they been in china?和how long have they learned Chinese?是现在完成时，基本构成是have done.变疑问句时要把have提前，后面的过去分词形式不变。 所以还是been和learned。