题目

We must work hard, and ______ we must believe in ourselves. A. in all                       B. above all                 C. after all                    D. at all 答案：B△ABC中，“A＞B”是“cosA＜cosB”的（ ）A．充分非必要条件B．必要非充分条件C．充分必要条件D．既非充分又非必要条件