1.A:I am sorry for coming late.
B:Don't be sorry.It's not you fault.I know that there is a traffic jam in this morning.
2.A:Is it okay with you if I borrow this book?
B:Yes,it's OK with me.
3.A:If you don't mind I wil open the window.
B:Not at all.
4.A:I'm sorry.I didn't realize you were eating dinner.
B:It doesn't matter.