A、Once a day. B、Twice a day. C、Once a week. D、Twice a week. B对话中，女士提到I have to do the cleaning twice a day(我一天要清扫两次)。故本题答案为B 。

M: So, how is your new roommate, Sarah?
W: She really turns me off, I have to say.
M: How come? Didn’t she move in just a week ago?
W: Yes, she did. But she’s driving me crazy. (19)She’s always making loud noises at midnight and when I remind her, she always makes rude remarks. What’s more, she would mess up the room, (20) and I have to do the cleaning twice a day.
M: That’s too bad. Haven’t you talk about it with her?
W: Of course, I have. But it didn’t work; she just pretended not to hear me. I’m thinking about complain to our instructor. I hope she will be forced to move out.
M: Well, good luck, then. By the way, where did your former roommate go?
W: You mean Jenny? (21) She went to America for further education. I learned from her email that she seemed to meet her Mr. Right on her vacation in California. I guess she may get married in a few months.
M: Oh, that’s so disappointing. Then I will have no chance to tell her how I feel.
W: Oh my God. Are you saying that you have feeling for Jenny?
M: I’m just kidding. But I do miss her. You know, she has done me a big favor last month. I was doing some shopping that day, but when I was at the cashier’s, I found I had left my wallet home. Luckily, Jenny was there. And it was she that helped me out.
W: I really miss her. I hope she could come back and live with me for another two years. She is so beautiful and considerate, totally different from my new roommate.
M: I agree.