it's +时间+since/that/when/before句型用法的差别它们分别有什么条件吗?

it's +时间+since/that/when/before句型用法的差别它们分别有什么条件吗? it's years since i It is+时间段+since+时间点那It's 9 o'clock 是时间段还是时间点 It's strange that the young man has kept () since last monthA,hiccupB,hiccuppingC,hiccupingD,hiccupped it's not all that long ago since ……中的all怎么理解? since引导的时间状语从句为什么出现在一般现在时里而不是现在完成时?我在这个句子里发现的：It's 20 years since he joined the party.既然有since了,前边为什么用It's呢? What was the party like Wonderful ,it's years () i enjoyed myself much.A after B beforeC that D since 我记得强调句的评判标准是去掉it's 和that 还能成句子,可是我没顺下来~请把顺下来的句子写下来.还有before +时间 it's +一段时间+since 是什么时态 it's been 39 days since you it's seems like years since it's been It's better that you grieve.It may not seem...It's better that you grieve.It may not seem that way since you want to appear strong in front of everyone It's said that the poor man——（lie）in bed since the end of last month It's almost three years ____ I last saw her.A.since B.when C.that D.after It's.that.造句 it's just that 关于since It's almost three years____I last saw her.A.since B.when C.that D.after答案是选A,但不是说since 只能用于完成时的吗?此题做何解释呢? That was really a splendid evening.It’s years _____ I enjoyed myself so muchA.when B.that C.before D.since 选什么? That was really a splendid evening.It’s years _____ I enjoyed myself so much.(2005安徽)A.when B.that C.before D.since为什么选D?