All living things on the earth need other living things to live with. Nothing lives   36  . Sometimes one living thing kills   37  . Each kind of life eats another kind of life   38   live, and together they form a food chain(食物链). Some food chains are simple, while others are not. But   39    food chains begin with the sun, and all food chains become   40   if one of the links disappears.

All life needs sunlight to live on. But only plants can use   41   directly(直接地). They make food from sunlight, water, air and so on. Animals can only use the sun’s energy   42    it has been changed into food by plants. Some animals feed directly on plants. Others eat smaller animals. Meat-eating animals are only   43 plants indirectly.

What about human beings? We are members of many food chains. We eat wheat, rice, vegetables, fruit and so on. We also eat meat and drink milk. But   44   often break up the food chains. They kill wild animals. They also make rivers, lakes and seas dirty. When these rivers, lakes and seas are polluted, the fish in them   45   be eaten. If people eat the fish, they will get strange diseases.

Each form of life is linked to all the others. Breaking the links puts all life in danger.

36. A. alone      B. lonely     C. together     D. happily

37. A. other      B. the other    C. another      D. the others

38. A. for       B. so that     C. and       D. in order to

39. A. any       B. all       C. some      D. most

40. A. better      B. broken     C. stronger     D. nicer

41. A. moonlight    B. laser light    C. sunlight     D. bright light

42. A. after      B. before      C. until      D. by the time

43. A. making     B. catching     C. eating      D. feeding

44. A. sunlight     B. animals     C. plants      D. people

45. A. can       B. cannot      C. must      D. needn’t

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