All living things on the earth need other living things to live with. Nothing lives  46  . Sometimes one living thing kills    47   . Each kind of life eats another kind of life     48    live, and together they form a food chain(食物链). Some food chains are simple, while others are not. But    49     food chains begin with the sun, and all food chains become    50    if one of the links disappears.

All life needs sunlight to live on. But only plants can use    51    directly(直接地). They make food from sunlight, water, air and so on. Animals can only use the sun’s energy    52     it has been changed into food by plants. Some animals feed directly on plants. Others eat smaller animals. Meat-eating animals are only   53 plants indirectly.

What about human beings? We are members of many food chains. We eat wheat, rice, vegetables, fruits and so on. We also eat meat and drink milk. But    54     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     55    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.

(   ) 46. A. alone         B. lonely         C. together         D. happily

(   ) 47. A. other         B. the other       C. another          D. the others

(   ) 48. A. for           B. so that         C. and             D. in order to

(   ) 49. A. any          B. all            C. some           D. most

(   ) 50. A. better        B. broken         C. stronger         D. nicer

(   ) 51. A. moonlight    B. laser light       C. sunlight         D. bright light

(   ) 52. A. after         B. before         C. until           D. by the time

(   ) 53. A. making       B. catching       C. eating          D. feeding

(   ) 54. A. sunlight      B. animals        C. plants          D. people

(   ) 55. A. can          B. cannot         C. must          D. needn’t