题目

— Do you think Andy can be a good policeman?        — Yes, I think so. He has the ability to stay when something dangerous happens.          A. calm             B. excited             C. afraid              D. nervous 答案：A如图所示，D，C，B在同一地平面的同一直线上，DC＝10 m，从D，C两地测得A点的仰角分别为30°和45°，则A点离地面的高度AB等于________;