如图，C岛在A岛的北偏东45°方向，C岛在B岛的北偏西25°方向，则从C岛看A、B两岛的视角∠ACB的度数是（　　）

阅读短文，下列问题

B

    Andy plays basketball for the children's basketball club. He usually gets up at around 5:30 and runs in his school from 5:40 to 6:40. After running, he has breakfast at 7 o'clock. For breakfast, he eats some eggs and vegetables. At around 8:00, he plays basketball with his friends. They play basketball for around four hours. At about 12:00, they have lunch. For lunch, Andy has lots of vegetables, chicken and fruit. At 3 o'clock in the afternoon, Andy goes to the children's basketball club. He is never late for the club. Then Andy has dinner at about 7:00. After dinner, he watches basketball games on TV. Andy usually goes to bed at 10:30.

民族区域自治制度是指在国家的统一领导下在少数民族聚居的地方实行区域自治，设立自治机关，行使自汉权的制度。以下对其理解正确的是（     ）
①是适合我国国情的一项根本政治制度         ②国家保障各少数民族的合法权利和利益
③有利于维护民族团结和国家统一                 ④在少数民族群众居住的地方都实行这种制度