题目

若函数y=可导,则“=0有实根”是“有极值”的（   ）A.必要不充分条件B.充分不必要条件C.充要条件D.既不充分也不必要条件 答案：AHe _____ a piece of waste paper, and put it into the rubbish bag. [     ]A. picked up B. put away C. threw away D. stood up