He's out on his lunch break right now.

不是on his lunch ,而是 on his lunch break ,在他的午休时间 的意思.所以必须用 on



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再问： 首先，谢谢您。另外，它原来的翻译是：“他出去吃午饭了”。还有：Now that it's almost time for my lunch break!快到午餐休息时间了。可这里用的是for啊?
再答： for 是“为了”。He's out on his lunch break right now. 人在某个时间出去吃午饭。在 用 on Now that it's almost time for my lunch break! 时间是为了吃午饭用的，所以用 for 要注意前边一句是“人”，一句是“时间”，不同。