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.

学习了电学知识后，小明、小亮和小艳所在的兴趣小组发现：电学量的变化往往能够用来反映力学、热学、光学等物理量的变化．在冯老师的点拨下，他们在探究过程中不断完善和优化方案，共同设计了一种用电学量的变化来反映力学量﹣﹣距离变化的装置．

①细胞无限分裂        ②水分减少，体积变小      ③畸形改变    ④酶活性降低      ⑤色素沉着      ⑥易分散转移    ⑦呼吸速度减慢         ⑧膜透性改变．