""is used for saying that what you do is more important than what you say you will do.( )
A.Every dog has its day
B.Practice makes perfect
C.Many hands make light work
D.Actions speak louder than words
已知集合,,则( )
如果复数为纯虚数,那么实数的值为( )
若函数在上的值域为,则称函数为“和谐函数”.下列函数中:①;②;③;④,“和谐函数”的个数为( )
已知正三棱锥的正视图、侧视图和俯视图如图所示,则该正三棱锥侧视图的面积是( )
已知是定义在上的偶函数,且当时不等式恒成立,若,,,则的大小关系是( )