题目

一艘海轮从A处出发，以每小时40海里的速度沿南偏东40°的方向直线航行，30分钟后到达B处，在C处有一座灯塔，海轮在A处观察灯塔，其方向是南偏东70°，在B处观察灯塔，其方向是北偏东65°，那么B，C两点间的距离是（ ）A.10海里 B.10海里C.20海里 D.20海里 答案：【答案】A【解析】先确定∠CAB和∠ACB,然后由正弦定理可直接求解.如图所示，易知，在△ABC中，AB＝20，∠CAB＝30°，∠ACB＝45°，根据正弦定理得＝，解得BC＝10 (海里)．故选：A阅读理解。My grandfather is fifty-five years old. He’s a taxi driver. He loves his job very much. It is Sunday. Today is his birthday. My father, my mother and I are in his house. My uncle also comes here. He is a tall man. He is a worker. He comes to see my grandfather every Sunday. My grandfather has a good friend. He’s name is Jim. He comes from England. He is a nice cook. He comes to see him, too. My grandfather is very happy today.【1】My grandfather is_____ years old now. ( )A. seventy B. eighty C. fifty-five【2】My grandfather is a_____. ( )A. worker B. driver C. cook【3】My_____ also comes to see my grandfather. ( )A. uncle B. aunt C. cousin【4】My uncle is very_____. ( )A. short B. fat C. tall【5】Jim is my grandfather’s_____ . ( )A. friend B. son C. daughter