下列变化属于物理变化的是（   ）

在R上定义运算：y=（2—y），若不等式（+a）＜1对任意实数都成立则                                                                  （ ）

阅读理解
    Mr. Black is American, but he is in Canada now. He is a tall man with funny glasses. He works in a big city but lives in a town far away. He lives on the twentieth floor of a building. Every morning he gets up early. Then he gets into the lift and it takes him down to the first floor. He runs to the bus stop and catches the early bus. It usually takes him about two hours to get to the factory by bus. Then he gets off the bus and walks into the workshop(车间) quickly. He starts his work at eight in the morning.

近年来，肇庆市在公办学校不能满足农民工子女入学的需要，普遍实行农民工子女教育积分制入学的管理办法。实行上述办法有利于（   ）

①消除城乡之间的差异                         

②消除社会不平等现象 

③维护农民工子女的平等权                     

④维护社会的公平和正义

已知m是8的相反数，n比m的相反数小2，求n比m大多少？