All these changes happened over a period of time.

　　所有這些變化都是在一段時(shí)間內(nèi)發(fā)生的。

　　You must on no condition tell them what happened.

　　你決不能告訴他們所發(fā)生的事。

　　This is the second time it's happened.

　　這已是第二次了。