这句话里用after还是since?

这句话里用after还是since? 这句话里since是什么词性? 这句话里用any还是many any怎么用 ever since,ever after since,before,after after,before,since after since when 用法 after the alarm had been given,请教这句话里的为什么要用given,given在这里怎么解 用before还是after? I will come back after two o'clock.这句话里的after能不能换成at?为什么?最好举 (it is ） four years since we last saw each other.这句话括号里为什么不是 请问Since then 和 After then 和 After that 这三个有什么区别啊?