单项选择题 企业破产倒闭导致持有该企业债券的理财计划所产生的风险是信用风险。( )

单项选择题 天然大理石按质量分为（）。

单项选择题 听力原文：M: I have been studying too much and need a change. So I have just made plans to go away during January break.W: Really? Where are you going?M: I'm planning to visit New Mexico.W: My sister and I had the vacation there last year and we had a great time.M: Did you get into Albuquerque?W: Sure. Whenever we went skating.M: Is it far from the mountains?W: Not at all. Even though Albuquerque is on a high flat plateau, there are even higher mountains near it. Just half an hour away from the city there is a snow-covered slope.M: Well. As the mountains are just thirty minutes away, I guess I should take my ice skate and my skis.W: Definitely.M: I heard that the weather there was great.W: It is 'No humidity' but with moderate temperatures, but you do need to be careful about high altitude.M: What should I do about that?W: Oh, just take it easy for a few days. Don't go hiking up the mountains or exercise too vigorously. Just do everything gradually.M: I'm sure I will be fine. And I will let you know all about my trip when I come back.What is the main purpose of the man's trip?A．To improve his skating techniques.B．To climb mountains.C．To take a vacation.D．To learn to ski.