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

SINCE TWO YEARS AGO的同义句 怎样理解I have had the bike for two years/since two years ago中的h two years ago 和for two years有什么区别 "two years ago "不是表过去时吗?为什么可以与现在完成时连用?(since two years ago)而 Lin Tao has been a teacher ()答案是since two years ago 为什么不能是si the swimming club opened two years ago（用since two years ago since two years ago与since two years的区别,分别用在什么时态? We-------students two years ago. Mr green has ()us English since two years ago They ___(live) there since two years ago How long ___ your mother ___?Since two years ago. Since they(visited/have visited)hangzhou two years ago,they(