在实数中2，0，﹣4，1，﹣2，最大的实数是（　　）

用反证法证明：若整系数一元二次方程ax²+bx+c=0（a≠0）有有理数根，那么a、b、c中至少有一个偶数时，下列假设正确的是（　　）

近年来，南海问题成为世界关注的焦点．当我们沿着历史的轨迹追寻国家兴衰之道时，就会深深感到正是海洋主宰着一个民族的盛衰荣辱．阅读下列材料回答问题：

材料一：l500年前后，世界终于冲破茫茫大海的阻隔，开始连成一个整体，海洋时代就此开启．然而中国，自郑和死后，中国人的身影就在海洋上消失了．从此，海洋带给中国人的不再是友谊和荣耀，而是噩梦的代名词，骨肉的离散与悲欢．

材料二：在内忧外患十分严重的形势下，清朝统治集团中的一些人认识到，要镇压人民起义，抵御外敌侵略以维护清朝统治，就必须学习西方先进军事技术．于是洋务派在举办近代工业的同时，用新式枪炮、轮船装备军队，改造陆军，建立新式海军．就这样近代意义上的中国水师（海军）诞生了，然而，随着北洋水师的全军覆没，中国水师不仅输给了日本，同时再次导致骨肉分离．

   Do you still remember the disaster(灾难)several years ago? In Indonesia (印度尼西亚) thousands of people were killed by the tsunami(海啸) that washed people out to sea and pulled children out of their parents’ arms. “The weather was fine with no clouds .There was no warning and suddenly the sea water just hit the city. In some parts the water was as high as two meters.” a man in the city said. “Sadli, an official at the hospital, said many of the dead in the city were children under the age of ten.” “Maybe the children were being carried by their hold but they fell over in the water and couldn’t hold on to their children .All the dead children drawed.” said Sadli. Officials said hundreds of houses had been swept away the force (力量) of five –meter –high waves across Aceh, which lies on the northern tip (末端)of Sumatra Island . “Tens of people saw the rushing water and didn’t run to high ground .Instead, they kept watching it .Several of my workmates are missing.”  Lelana said by telephone.