题目

——Mary hasn’t paid for the school things , has she ? ——_________. Her mother will pay for her . A．Yes , she hasB．No , she hasn’tC．Yes , she didD．No, she didn’t 答案：B解析:略如图，AB是⊙O的直径，弦CD⊥AB，垂足为E，如果AB=20，CD=16，那么线段OE的长为（ ）A．10B．8C．6D．4