在设计对照实验时，我们应注意的问题是（　　）

阅读理解

    Every country has its favourite food. In some countries, people(人们) eat rice every day. They often eat it with meat, fish and vegetables.       

   Japanese(日本人) eat a lot of fish, and they eat a lot of rice, too. In England(英国), the favourite food is fried fish and French fries. In the USA(美国) people like hamburgers a lot. And they like to have cold drinks. In Canada, people eat bread with butter(黄油) on it. In India, people like to eat hot food. Some people eat only fruit and vegetables. They don't like to eat meat and fish. They think green food is good for them.

阅读材料，回答下列问题。

材料一  下图为我国“十二五”规划综合能源基地示意图。

材料二  下左图、下右图分别为新疆基地、西南基地矿产能源分布图。