用 “It has been +一段时间+since”造句两个

用 “It has been +一段时间+since”造句两个 It is 一段时间 since 后面可以现在完成时吗It is +一段时间 +since + 一般过去时It has been +一段时间 +since +一般过去时这两种是可以的,那 since 后面除了一般过去时,可以用现在完成时吗? since的用法 it+is+一段时间+since+从句为什么这里is可以换成has been但不能换成was it has been two day since we left our hometown为什么用has been如题 it has been since.用法 It has been in my it is/has been= It's has been accepted it has long been assumed It is/has been+since sb+did 怎么用? how long since i bumped into you and your sister at McDonald?选项：A is it B was it C had it been D has it been it is +加一段时间 since 与 it has +加一段时间 since 不是意思一样吗?我很混,请问此题该作何解？ it's always been you(It has always been it has been可以缩写成it's been it's been.的全称是不是 it has been... it has been very cold this year 为什么用been 启一个什么作用 throw是不是非延续性动词?那它的完成时有一段时间的话怎么变it has been a while since i threwn that stone. Believe it or not,Jack has been to Beijing.为什么要用has been to,不用was to It has been suggested that girls avoid mathematics course for social reasons.为什么用has been suggested 什么结构?