单选题
Everything living on earth each plant and animal needs other living things. Nothing lives alone. Most animals must live in a group, and even a tree or a plant grows close together with othersof the same kind. Sometimes one living thing hunts another, one eats and the other is eaten. Eachkind of life eats another kind of life in order to live, and together they form a food chain. Somefood chains are simple, others are complicated. But all have two things in common-all foodchains begin with the sun, and all food chains become broken up if one of the links disappears.
All life depends on energy from sunlight. Only plants can use this energy directly. Their leaves are little factories that use sunlight to make food from water and things in the soil and air.
Plants in turn feed all other living things. Animals can only use the sun’s energy after it has been changed into food by plants. Some animals feed directly on plants, others eat smaller animals.Meat-eating animals are only eating plants indirectly.
What about human beings? We are members of many food chains. We eat wheat, rice, vege-tables, fruits and so on. We also eat meat and drink milk. This means the sun’s energy passesthrough plant to animal before it reaches us.
Nature is a greater thing. Any food chain always produces enough for each of its members if itis left alone. When there isn’t enough food for any link in the chain, some of its members die off.So the balanee is always kept.
But men in their greed and ignorance often break up the food chain and do great harm not onlyto one plant or animal, but to all the links in the chain. People make seas and rivers dirty. They de-stroy whole forests and kill many kinds of wild animals and birds. When a river becomes dirty, thefish cannot be eaten. Men eat the fish and get strange diseases. In some places men have no fish toeat any more, because the fish have died off. Each form of life is linked to all others. Breaking thelinks puts all life in danger.
单选题
How does everything living on earth live?
【正确答案】
C
【答案解析】细节题。根据第一段第一句“Every thing living on eanh each plant and animal needs other living things”可知，地球上的万物，不论动物还是植物，都依赖于别的生物，也就是说，没有其他的生物，地球上的任何一种生物都无法生存。因此答案为C。
单选题
How is food for plants made? Food for plants is made______
【正确答案】
D
【答案解析】细节题。根据第二段中“Only plantscall Bse this energy direcfly．Their leaves are littie factories that use sunlight to make food fromwater and things in the soil and air．”可知只有植物能直接利用阳光。植物的叶子就像是小工厂，它们利用阳光、水、土壤和空气里的东西制造食物，即植物的食物是由阳光、水、土壤和空气里的东西制成的。所以此题选择D。
单选题
How do all food chains break? All food chains are broken if______
【正确答案】
D
【答案解析】细节题。根据第一段最后一句“and all food chains become broken up if one of the links disappears”可推知如果一个食物链中的链条被破坏，整个食物链就断了。所以此题选择D。
单选题
Which living things can use energy directly?
【正确答案】
B
【答案解析】细节题。根据第二段中的“Only plantscall use this energy directly”可知答案为B。
单选题
Why is all life in danger? Becausebreak up the food chains.
【正确答案】
A
【答案解析】推理判断题。根据最后一段第一句“But men in their greed(贪婪)and ignorance(无知)often break up the food chain”可推知是人的无知和贪婪破坏了食物链。根据最后一句“Breaking the links puts all life in danger．”可知破坏食物链会使所有生命处于危险之中。因此可推知所有生命处于危险之中是因为人类破坏了食物链。所以此题选择A。