— did the cartoon book cost you? —Five dollars. A. How long B. How much C. How many D. How often 答案:B17.函数f(x)是定义在R上的偶函数,其导函数为f′(x),当x<0时,3f(x)+xf′(x)<0恒成立,则下列结论正确的是( )A.f(1)<2016f($\root{3}{2016}$)<2017f($\root{3}{2017}$)B.2017f($\root{3}{2017}$)<f(1)<2016f($\root{3}{2016}$)C.2016f($\root{3}{2016}$)<f(1)<2017f($\root{3}{2017}$)D.2017f($\root{3}{2017}$)<2016f($\root{3}{2016}$)<f(1)