设为△内一点,若,有,则△的形状一定是( ) A.锐角三角形 B.直角三角形 C.钝角三角形 D.不能确定 答案:B 解析: 由题设得,,再由向量的几何意义易知,,故选B.— Do you have any good ways to increase the reading speed?—Yes, try to guess its meaning when you meet a new word. Don’t ________your dictionary all the time.A.keep on B.work on C.depend on