阅读下列短文，从每题所给的A、B、C、D四个选项中选出最佳答案。

    All living things need energy to live and grow. This energy comes first from the sun. Plants use water and sunlight to make their own food. Animals can not make their own food, and they eat plants. Other animals then eat the plant eaters.

    A food chain shows what eats what. It might show that zebras eat grass and then lions eat zebras.   

    Lions also eat other animals. Zebras eat other kinds of plants. So it takes more than one food chain to show how lions and zebras get their energy.

    A food web shows how food chains work together. From it we can see how energy moves from plants to animals.

    Plants and animals that live in hot, dry deserts depend on water as well as food. Creosote bushes have small leaves that hold water. Their seeds provide food and water for kangaroo rats. Kangaroo rats don't need to drink water. They get all the water they need from the plants they eat. Kangaroo rats keep cool by coming out only at night to look for food. Ringtail cats also come out only at night. Ringtail cats hunt and eat kangaroo rats. Coyotes eat both the kangaroo rats and the ringtail cats.

    Nothing is wasted in a food wed. Vultures eat dead animals. Vultures are scavengers. Scavengers do not hunt and kill other animals to get food. They eat animals that are already dead. When a ringtail cat or a coyote dies, it makes a meal for the vultures. Scavengers do an important job in keeping the environment clean.