“最美志愿者”王晰昧，毕业于名牌大学，任职于知名企业，但就在事业成功的关头，毅然辞去沿海城市年薪百万的工作，来到新疆生活条件最艰苦的帕米尔高原义务支教，用自己的学识打开贫困牧区孩子的心灵之窗。她的事迹说明（    ）

①热心公益，在奉献中提升自身的价值

②义务支教、服务社会，是我们义不容辞的法定义务

③不计较代价与回报的奉献精神，是社会责任感的集中表现

④参与社会公益活动，有利于营造“我为人人，人人为我”的社会氛围

阅读短文，下列问题

      A boy goes to the cinema. He buys a ticket and goes in. But after two or three minutes he comes out. He buys a second ticket and goes in again. After a few minutes he comes out again and buys a third ticket. Two or three minutes after that he comes out the fourth time and asks for another ticket. The girl says to him, “Why are you buying all these? Are you meeting friends in the cinema all the time?”

     “No, I'm not doing that,” the boy says. “But a big woman always stops me at the door and tears(撕掉) my tickets.”

配方法解方程x²-4x+2=0，下列配方正确的是（    ）

化学上把同种元素组成的不同单质叫做同素异形体，如金刚石好石墨。下列各组物质互为同素异形体的是（  ）