①對(duì)數(shù)函數(shù)與指數(shù)函數(shù)互為反函數(shù)；②指數(shù)函數(shù)y=a^x(a＞0且a≠1)的圖象關(guān)于直線y=x對(duì)稱的圖象，就是相應(yīng)的對(duì)數(shù)函數(shù)的圖象；③底數(shù)0＜a＜1時(shí)的指數(shù)函數(shù)是減函數(shù)，底數(shù)0＜a＜1時(shí)的對(duì)數(shù)函數(shù)也是減函數(shù)；④底數(shù)a＞1時(shí)的指數(shù)函數(shù)的圖象都在直線y=x的上方，底數(shù)a＞1時(shí)的對(duì)數(shù)函數(shù)的圖象都在直線y=x的下方.

A.①②③          B.②③④             C.①③④          D.①②③④

將指數(shù)與對(duì)數(shù)互化:

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