The mountain I visited last Sunday isn't very ___________. Few ___________ go sightseeing there.
①∃a∈R,使f(x)为偶函数;
②若f(0)=f(2),则f(x)的图象关于x=1对称;
③若a2﹣b≤0,则f(x)在区间a,+∞)上是增函数;
④若a2﹣b﹣2>0,则函数h(x)=f(x)﹣2有2个零点.
其中正确命题的序号为____.
能卷舌和不能卷舌是一对相对性状,分别由A和a控制,下列叙述中不正确的是( )