《管理生命之序》这篇文章告诉我们，合理利用时间要（  ）

    What do you eat every day? Some people think about it. And some people will not make plans for their meals.

    Many people like to have fast food near their offices. This kind of food can make them fat and it is bad for their health. Even it will make them ill when they are old.

   What should a healthy person eat every day? Well, I will tell you the 'healthy eating habit(习惯)'. It comes from doctors.

     When people do a lot of work, the energy is burning(燃烧). So you need noodles, rice, milk, bread and eggs. If you don't eat them, you will feel tired. You should eat fruits and vegetables, too. There are a lot of vitamins（维生素） in them. They can make you strong. And they can give you water.

为体现低碳经济的理念，上海世博会充分利用太阳能发电技术，其主题馆屋面太阳能板的面积达3×10⁴m²，年发电量3×10⁶ kW·h．若这些电能由火力发电站提供(煤的热值为3×10⁷J／kg，煤完全燃烧释放的内能转化为电能的效率是30%)，则仅此一项每年可节约煤炭的质量为（）