had been 是 was 的过去式吗

had been 是 was 的过去式吗 been是be的过去式吗? must have been在主句是一般过去式的宾语从句中变为must had been吗 ?两小时内给出答案 is的过去式是was be动词的过去分词是been been是动词吗?如果是,它的过去式是什麽? 下面句子为什么用的是被动语态was finished而不是过去完成时had been finished As no pumas had been reported missing里面的had been能不能换成was呢? was done和had been done的区别 was和had been是什么关系 过去完成时吗? been的过去式 have been 的过去式? had的过去式