题目

-Let's play computer games. - ________. A. It doesn't matter B. No, I don't C. That sounds really boring D. It's nothing 答案：C 如图，一条小船从港口A出发，沿北偏东40°方向航行20海里后到达B处，然后又沿北偏西30°方向航行10海里后到达C处．问此时小船距港口A多少海里(结果精确到1海里)？(参考数据：sin40°＝0.6428，cos40°＝0.7660，tan40°＝0.8391，≈1.73．)