函数的导数=（   ）

(单选题)19. （ ） (单选题)18.（ ） (单选题)17. （ ） (单选题)16.（ ） (单选题)—______ are these apples?—$ 3.99. (单选题)In front of the whole class, he made his promise ______ he w (单选题)We don’t understand the passage ______ there are a few new w (单选题)The desk is light. I can carry it ______. (单选题)I can’t find my cat. Could you help ______ find it? (单选题)坐标满足，且，，则的最小值为（ ）。