[单项选择]

A
Everything living on earth--plants and animals need other living things. Nothing lives alone. Most animals must live in a group, and even a tree or a plant grows close together with others of the same kind. Sometimes one living thing hunts another; one eats and the other is eaten. Each kind of life eats another kind of life in order to live, and together they form a food chain. Some food chains are simple; others are complicated. But all have two things in common--all food chains begin with the sun, and all food chain 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. Me
A. Animals.
B. Plants.
C. Both animals and plants.
D. All living things.