by the time the earthquake ended,millions of people had become homeless.为什么加had?直接became可以吗？

Venus is the ( )plant to the eart puzzle to the center of the eart怎么玩 by the time ,by then By the time by the time 用by the time造句! by the time怎么造句? by the time +现在式造句 by the time 的用法 by the time 等于什么? by the time to 谢 by the time什么意思 the time,show by the day on the time ,in the time ,at the time ,by the time on the time ,in the time ,at the time ,by the time as the time goes（went) by,with the time going byas the time goes by,with the time going by,as the time went by,用于什么时态? by the time of和by the end of in time ,on time ,by the time 的区别,