叶绿体和线粒体都是植物细胞内的能量转换器，它们的作用有什么不同？

    Food waste has become a big problem in China.
   Zhou Jinsong, a canteen(食堂) manager at Central South University, said that students produce over 12 barrels(桶) of leftovers every day — each barrel stands at one meter in height. Zhou’s canteen is just one of several on the campus.
   According to Xinhua News Agency, the food wasted by Chinese people equates to about 50 million tons of grain every year, or 10 percent of the country’s total annual grain production. This food could feed another 200 million people. What students waste every year could feed over 10 million people. Students nowadays are well protected by their families and hardly know how hard farmers work to provide them with the food they eat.
   “Since the 1980s, when Chinese gradually became richer, food waste has been a subject of debate. But things have hardly changed over the years,” said Yu Changjiang, a sociologist at Peking University. “It’s the Chinese way of showing respect to friends, often referred as Mianzi.”
   But rather than tradition, huge public spending on government banquets(宴会) is also causing food waste, said Zhou Xiaozheng from the sociology department at Renmin University of China. “It’s the result of widespread reception meals at government levels. It is also important that everyone thinks about how they can do their best to reduce food waste.”

中国历史上由少数民族建立的统一的全国性政权是（     ）

①唐朝          ②宋朝        ③元朝

④明朝          ⑤清朝

①海水淡化可缓解淡水资源匮乏问题。水变成水蒸气的过程，从微观角度分析发生变化的是____。

②生活中用到的食盐主要来自于海水。“海水晒盐”所采用的方法和实验室里____操 作相似。得到的粗盐中通常含有 Na₂SO₄、CaCl₂、MgCl₂等杂质，其中 Na₂SO₄也是白色固 体。我们可以用不同的方法鉴别 NaCl 和 Na₂SO₄。

方法一：根据两者酸根不同，选择____试剂进行鉴别。

方法二：查得两者在不同温度下的溶解度（单位：g/100g 水）。

称取两种白色固体各 3 克分别放入 A、B 两个烧杯中，再分别加入室温（20℃）下 10mL 水(水的密度为 1g/mL)，充分搅拌后如下图所示：

烧杯 A 中溶质质量分数为____（用相应的数据列式表示，不必计算），烧杯 B 中未溶解的物质是____，由此鉴别出这两种物质。以上方法利用的是： NaCl 和 Na₂SO₄在室温时的____不同。根据上表信息，在____温度范围内可能无法用上述方法鉴别这两种物质。