25. They suggested that the professor ______ just now ______ chairman of the meeting.

A．referring to; was made

B．referring to; be made

C．referred to; be made

D．referred to; was made

已知函数f(x)=x²-cosx，对于

上的任意x₁，x₂，有如下条件：
①x₁＞x₂；

；③|x₁|＞x₂。
其中能使f(x₁)＞f(x₂)恒成立的条件序号是（）。