[用can提问进行询问或征求同意]

肯定回答

Can I open the window in here?
– Sure, go ahead.（go ahead（用于给别人许可）进行，开始，做）
– No problem.
– No worries.
– Yes, sure.
– Yes, of course you can.

Can you help me?
– Of course！
– Sure！
– Certainly！

否定回答（拒绝对方）
Can I open the window in here?
– Actually, I'd prefer it closed. 其实，我想关着窗子。（actually 其实，说实话，实际上（用于礼貌地表示反对、纠正他人或拒绝他人提议等））
– I'm sorry, but I'm cold. 不好意思，我有点儿冷。

Can we sit here?
– Sorry, the seat's taken. 抱歉，座位有人了。
– I'm sorry, but you can't. Someone else is sitting here. 抱歉，（你们）不能（坐这）。有人坐这了。