12．All living things on the earth need other living things to live．Nothing live alone．Most animals must live in a group，and even a plant grows close together with others of the same kind．Sometimes one living thing kills another，or one eats and the other is eaten．One kind of life eats another kind of life in order to live，and together they form a food chain（食物链）．All food chains begin with the sun，and all food chains become broken up if one of them disapp ears．
All life needs sunlight to live on．But only plants can use sunlight directly．Plants are"factories"．They make food from sunlight，water and things in the soil and air．
Plants feed all over living thing．Animals can only use the sun's energy （能力） after it has been changed into food by plants，some animals feed directly on plants，other eat smaller animals．Meat-eating animals are only eating plants indirectly．
What about human beings？We are members of any food chain．We eat ice，vegetables，fruits and so on．We also eat meat．But men often break up the food chain．They kill wild animals．They also make rivers，lakes and seas dirty．When these river，lakes and seas are polluted，the fish in then cannot be eaten．If men eat the fish，they will get strange disease．
Each form of life is linked（联系） to all others．Breaking the links puts all life in danger．
41．Food chains suggest thatC．
A．every life needs food．
B．plants are very important
C．no living thing can live alone．
D．living things need different food．
42．From the text we can learn that the sunC．
A．forms a food chain
B．makes animals to grow fast
C．is the beginning of food chains
D．is directly giving us different food
43．What do plants need to grow up？B
| a．living things b．soil c．water d．sunlight e．things in the air |
A．a；b；c；d
B．b；c；d；e
C．a；b；d；e
D．a；c；d；e
44．Which can change the sun's energy into food？A
A．Plants
B．Humans
C．Plant-eating animals
D．Meat-eating animals
45．The writer is trying to tell us not toB．
A．kill animals．
B．break the links of life．
C．worry about food chains．
D．eat fish from polluted water．
