为什么是since two years ago 而不是for two years ago

为什么是since two years ago 而不是for two years ago SINCE TWO YEARS AGO的同义句 since two years ago与since two years的区别,分别用在什么时态? it is five years since we began learing English 为什么是it was When did you study in france?A,Two years ago B,Since two years ago the actor and director_______(move) abroad since two years ago. The story factory___(open)since two years ago. Tom has been on the island since two years.(改错) Mr green has ()us English since two years ago mary has got married since two years ago改错 since two years ago 它是一个时间点 还是一个时间段? Dave __ (learn) Chinese since two years ago it is two years since I came here还是it has been two years since I came here mei lin has been a teacher ---.a.since two years b.since two years ago 为什么选b? Her grandmother has been dead for two years 为什么是Her grandmother has been dead for two years 为什么是用dead形容词,而不是died 不是现在完成时吗? the swimming club opened two years ago（用since two years ago 改写)the swimming club ____ ____ ____ since two years ago. ever since 和since 有什么区别Mr li went to America 20 years ago and has bee there ever since.后面为什么是ever since?不是ever since要和现在完成时连用吗?这里怎么会是过去时态啊? It's two years since he left his hometown.since 为什么不能换成after