As a result of many years’ hard work,his father has completely in health. A. broken through B. broken down C. broken up D. broken away 答案:B给出下列四个命题:①若函数f(x)=a(x3-x)在区间(-33,33)为减函数,则a>0;②函数f(x)=lg(ax+1)的定义域是{x|x>-1a};③当x>0且x≠1时,有lnx+1lnx≥2;④若M是圆(x-5)2+(y+2)2=34上的任意一点,则点M关于直线y=ax-5a-2的对称点M′也在该圆上.所有正确命题的序号是