题目

下列运算正确的是（ ）A.（ax2-bx+c）′=a（x2）′+b（-x）′B.（sinx-2x）′=（sinx）′-（2）′（x）′C.（cosx5sinx）=（sinx）′cosx+（cosx）′5cosxD.（）′= 答案：解析：由和与差的导数运算法则可得A正确.选A.答案：A–Guess what! Alice has failed in the exam. – ____? She is second to none in English in our class. A．How is itB．How comeC．WhatD．What is it