A、Through email. B、By telephone. C、Write comments to them. D、Meet them face-to-face. D男士说到，虽然可以用电邮与同事交流。但他更喜欢面对面的交谈。即D。

M: Today time has gone by so quickly! Do you estimate how long a job will take?
W: Well, sometimes it’s not productive for me to estimate how much time I will spend completing a job.
M: That’s true, but in order not to waste time, I always want to set a precise time to meet someone.
W: If I have an appointment. I try to figure it out how much travel time is involved.
M: I find it really difficult to stay on a time plan when I go to a convention.
W: Why is that?
M: Because I meet so many new people, and I want to interact with them.
W: A convention is a good place to enquire with them professionally.
M: Yes, although I can communicate with many of my colleagues through email. I would prefer to chat with them face-to-face.
W: That would fulfill my needs better because I wouldn’t have to write out my questions or comments.
M: Well, by the way I have noticed that many people in China travel to work by bicycle.
W: Yes, it’s convenient most of the time because the traffic is often very bad.
M: But it would not be possible for me to ride to work in the United States by bicycle because I live a long way from work.
W: Of course not! Also, parking a car in Shanghai is a problem, so when I really need to get somewhere quickly, I sometimes take a taxi.
M: In my city in the United States, you have to telephone a taxi if you need one.
19. What does the woman want to know if she has an appointment?
20. What is the man’s favorite way of communicating with colleagues?
21. Why does the man say it is impossible to go to work by bike?