下列固体中属于晶体的是（　　）

    The "green" car has become popular in recent years. A green car is an environment friendly car. Today, most cars are powered (驱动) by petrol (汽油). They make our life easier. But cars have also made problems for the environment.

    There are a few new types of cars that use no petrol or a little petrol.

    Electric cars：This kind of car uses a battery (电池) for power. When you're not driving it, just plug it in like a mobile phone to power up the battery. They don't make exhaust (排放物). But car makers still can't make a battery that lasts for more than a few hours. That's why electric cars aren't very popular.

    Fuel cell cars (燃料电池车) : Fuel cell cars use hydrogen (氢) and oxygen (氧) to make power. The only exhaust they produce is clean water. But fuel cell cars are still much too expensive to make.

    Solar cars : This kind of car has large panels (板) on the top that take power from the sunshine. The car holds that power in a battery. Solar cars might be the cleanest of all. But no one uses them, because solar panels can't get enough power from the sun to make a car go for a long time. Also, they are very slow.

    Hybrid cars（油电混合车）： This kind of car is the most exciting kind, because it is very clean and not too expensive. The hybrid car is very smart: Half the time, it uses petrol, and half the time it uses a battery. So, when the petrol engine is working, it puts some of its power back into the battery. It uses much less petrol than other cars. It also makes less pollution for the environment.

保护生物多样性最为有效的措施是（　　）

下列语句出自不同时期的历史文献或历史人物之口，其中分析不恰当的是(  )

甲：“戮力本业，耕织致粟帛多者，事末利及怠而贫者，举以为收孥。”

乙：“凡士、工、商贾，皆赖食于农，故以农为天下之本务，而工贾皆其末也。”

丙：“商籍农而立，农赖商而行。”

丁：“世儒不察，以工商为末，妄议抑之。”