--i'm sorry to keep you waiting i'll make short of work of t

--i'm sorry to keep you waiting i'll make short of work of this.--_____.i'm not in a hurry.
--i'm sorry to keep you waiting i'll make short of work of this.
--_____.i'm not in a hurry.
A.take it easy B.take your time C.not at all D.bo as you like
答案选B,为什么?这四个选项分别用在什么情况下?