题目内容：

have been 与had been
在遇到什么局子时have been 改用had been

优质解答

have been变成had been的情况一般出现在宾语从句中.因为宾语从句的时态要与主句谓语动词时态一致.比如：He has been in China for 4 years.这是has been.但变成宾语从句的时候,如果主句是过去式,这里也要变成had bee...