题目

 _____ of water makes Death Valley a desert, but it is by no means devoid.        A. Lacking     B. Being lack        C. Because of lack   D. Lack 答案：D如图，AD为△ABC外接圆的直径，AD⊥BC，垂足为点F，∠ABC的平分线交AD于点E，连接BD，CD．（1）求证：BD=CD；（2）请判断B，E，C三点是否在以D为圆心，以DB为半径的圆上？并说明理由．