I'm taking a test and have to guess the right answer to the question after the article. Article: As I was leaving to meet Lynne, my roommate told me that I'd better take some money. But I didn't listen to him. I thought that Lynne would pay because she had invited me. I arrived at the restaurant exactly on time. I'd been told that Americans expect you to be on time. Lynne and I sat at a table in the corner of restaurant and a waitress came and took our order. The dinner was a great success. I talked a lot about Saudi Arabia and Lynne told me all about herself. After two hours, the waitress finally came and asked if we wanted one check or two. Lynne said two. We went to the cashier and Lynne paid her check. I was embarrassed when the cashier gave me my bill. I had no money to pay for my meal. Then I had an idea. I pretended to look for something in my pockets and said, "Oh! I forgot my wallet! Can I call my roommate, please?" The cashier showed me where the phone was and I quickly called my roommate. In a few minutes, he arrived with some money, but he couldn't hide how he felt. He laughed all the way home. Now, I think it's funny too, but at that time I was terribly embarrassed. I thought that an invitation to have dinner in the United States meant the same thing as that in China. I guess you have to understand that your customs are only your customs. When you visit a foreign country, you have to learn about their customs, too. Question: What is the passage mainly about? Options: A: People should always take some money with them. B: A Chinese man must pay for the meal. C: A good roommate can really help you a lot. D: Customs can be entirely different in different countries.
D