have/has是完成时,后面加been再加过去分词.
were/was是过去式,后面直接加过去分词.
用完成时还是用过去式得看句子的时间状语或根据上下文.
例句：The e-mail was sent to him yesterday.
The e-mail has been sent out.
The books have been read.
The articles were written by the famous writer.
总之,完成时强调过去动作对现在的影响,而过去式强调过去已经完成的动作,不强调过去对现在的影响.