一、完形填空
阅读下面短文，掌握其大意，然后从以下题所给的A、B、C、D四个选项中，选出最佳选项。
Every living thing in an ecosystem depends in some way upon other living and nonliving things in the ecosystem.
The living things in an ecosystem are 1.________ producers or consumers. Producers don't eat other living things. Producers make food. Green plants are called primary producers. Plants use nonliving nutrition，such as 2.________ chemicals in soil and water to help them make food. They use energy in sunlight to make food. They also use carbon dioxide in air to make food.
