it's doesn't matter.Not at allThat's all rightNo problemYou are welcome.Never mind,That's OKIt's nothing在日常用语中的口语常用 i don't care(我不介意或没关系)其他的也可以,但是不够专业显的补礼貌...
对不起 : I am sorry, Sorry, (I am)sorry to interrupt/trouble you. Excuse me, but ... Pardon, can you ... etc. 没关系: Not at all. That's all right. Never mind! Forget it.