题目

We arranged to meet at the cinema at 7:30, but he failed ______ up. A . turning B . turns C . turned D . to turn 答案：D下列命题中：①集合{x|1+x＜4，x∈N}是有限集，集合{x|x2+1=0，x∈R}是空集；②函数y=logx-1|x|的定义域为（1，+∞）；③函数是奇函数；④若方程（lgx）2-（lg2+lg3）lgx+lg2lg3=0的两根为x1、x2，则x1x2=6正确命题的序号是________．