竞技之路启迪人生。与王治郅的对抗进一步点燃了姚明对篮球的热情，他说：“只有和最强的人对抗才来劲。”这句话告诉我们（    ）

在日常生活中如取款、上网都需要密码，有一种用“因式分解法”产生的密码方便记忆，例如，对于多项式x⁴﹣y⁴，因式分解的结果是（x﹣y）（x+y）（x²+y²）．若取x=9，y=9时，则各个因式的值为（x﹣y）=0，（x+y）=18，（x²+y²）=162，于是就可以把“018162”作为一个六位数的密码，对于多项式x³﹣xy²，取x=20，y=10，用上述方法产生的密码不可能是（　　）

已知sinα﹣cosα=$\sqrt{2}$，α∈（0，π），tanα=____ 

    It seems that Chinese people have always loved to discuss ____ differences between northerners and southerners. Now, another difference has drawn wide attention: the way northerners and southerners shop for food at markets.

    People from southern China normally buy ____they need for just one or two meals at a time. It's normal for them to buy just half a Chinese cabbage, two ____（potato）and 25 grams of beef at a time, ____， a person may be laughed at if they do this in the north. Instead, buying enough vegetables and meat for a week ____（be）normal.

    The difference could be because ____the different climates. Food can ____（keep）for a long time in the north, as it's ____（usual）cold and dry there. Many northerners have the habit of ____（store）food for a long time. But due to the hot and wet weather in the south, southern Chinese people prefer ____（buy）just enough food for one meal or one day. Otherwise, the food may go bad.

    Maybe these debates about different customs help us to understand each other better.