1. I´ve already had lunch.
    我已经吃过饭了。

2. I had lunch at half past twelve.
    我在12点半吃的。

3. I had one after my lunch.
    我是在饭后喝的。

4. Insulted, I throw my lunch into the trash barrel and let Sam lead me to the swings.
    我觉得受了侮辱，于是把午饭扔进垃圾桶里，随山姆来到了秋千旁。