题目

We are sure to fulfill       promise we made to the world: The Beijing Olympic Games will be       green event. A．the; /               B．the; a               C．the; the            D．a; a 答案：B已知α，β为不重合的两个平面，直线m?α，那么“m⊥β”是“α⊥β”的（ ）A．充分而不必要条件B．必要而不充分条件C．充分必要条件D．既不充分也不必要条件