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. How do all food chains break All food chains are broken if______

A. one kind of animal is eaten up
B. one kind of plant is destroyed
C. one kind of animal eats another
D. one of the links is destroyed