单项选择题

M: So you’re visiting San Francisco
W: Yes, I just got here the day before yesterday, and you
M: I’m a native.
W: Oh, really All the people I meet here are tourists like me. I was beginning to think that maybe there were no natives.
M: Well. San Francisco has a lot of different ethnic groups, so you might think you’re seeing a lot of foreigners. But in fact, the city has a population of about 700, 000 people.
W: What are the ethnic groups
M: Well. after whites, the largest one is blacks.
W: I thought it was Chinese.
M: It’s true that San Francisco has the largest Chinese community outside Asia. But the black people there are more than Chinese.
W: That’s interesting. Don’t most of the Chinese people live in Chinatown
M: Well, no, they live throughout the city, but Chinatown is definitely the center of Chinese culture here. That’s where you’ll find the best Chinese restaurants, bookstores, art theaters and things like that.
W: How about the Japanese Doesn’t San Francisco have a large Japanese population too
M: No, actually there are only about 12,000 Japanese people here, but we do have an area called "Japan town" that has Japanese restaurants and bookstores.
W: You seem to know a lot about this city.
M: Well, most San Franciscans think their city is pretty special. We like to talk about it. Besides, I teach ethnic history at the university here.
W: No wonder you know so much!

Why does the man know so much about San Francisco()。

A. He thinks the city is pretty.
B. He likes to talk with people.
C. He travels a lot in the city.
D. He teaches ethnic history at a university.