before到底是之前，還是之後？
1. It won't be long before he returns to his native land.
他不久後就會回到祖國。
2.If you miss this chance it will be years before you get another one.
如果失去了這次機會，要許多年以後你才能有這樣的機會。
3. A whole month had passes before he fully recovered.
他一個月之後才完全康複的。
