present perfect 为什么有些要加been?例如：has been built has sent

present perfect present perfect simple and present perfect continuous Present simple,present continuous,present perfect simple,present perfect continuous present perfect continous是什么 present perfect是什么意思 The present perfect tense present perfect progressive 现在完成进行 和present perfect 有什么区别present perfect 加has/have+past participle 而present perfect progressive has/have+been+verb+ingparticiple 过去分词 英语present perfect simple跟past perfect simple 有什么区别? present perfect;：indefinite past有一本英语语法书现在这个单元是 present perfect：indefinite past 请问这是什么语法?我想知道这个单元要讲的是什么意思 因为已经讲过present perfect了,为什么还要加一个i 请问present simple,the present continuous,the present perfect这三个之间有什么区别么?怎么分别他们 请问present/past perfect tense 跟present/past perf请问present/past perfect tense 跟present/past perfect continuous tense 有何分别?当做时态练习时,如何清楚介定它们.（它们有哪些标示语） 什么是PRESENT PERFECT CONTINUOUS啊? present perfect 为什么有些要加been?例如：has been built has sent write the sentence in the present perfect 用present perfect tense ,simple past tense , 求 4 个 present perfect progressive 句子 求 4 个 present perfect progressive 句子.. the present perfect tense的中文