I have to work on sunday.
我星期天得上班。
A: Can we meet for lunch on sunday?
A: 星期天大家能一块吃午饭吗？
B: No, I'm sorry. I can't. I have to work on sunday.
B: 对不起，不可以。我星期天得上班。
A: Oh, that's a pity. I forgot you sometimes work at weekends.
A: 哦，太遗憾了。我忘了你有时周末加班。
B: We could go for lunch on saturday, if you'd like.
B: 周六大家可以一块吃午饭，假如你想的话。
A: Yes, that'd be good. Let's do saturday instead.
A: 好，可以。那大家就改在周六了。
Notes 注解1. When someone asks you a question beginning Can you . . ? / Can you . . ?, the simple response is usually Yes, I can / Yes, I can or No, I can't / No, I can't.
当有人问你以Can you . . ? / 你能 . . 吗?开头的问题时，简单的回答是Yes, I can /是的，我可以。或者No, I can't /不，我不可以。
2. Remember various phrases1 to describe times, eg at the weekend / at the weekend: another day / another day: during the week / during the week: on tuesdays / on tuesdays.
记住用不一样的短语来描述不一样的时间段。比如at the weekend /在周末；another day /另一天：during the week /在这周内: on Tuesdays /在周二。
3. If you are talking about a possibility, you can use could / could, eg We could go for lunch / We could go for lunch: It could rain tomorrow / It could rain tomorrow.
假如你在谈论某种可能性，你可以用could / 可能。比如We could go for lunch /大家可以一块吃午饭。It could rain tomorrow /明天或许会下雨
