听力原文：
Most of us think that people are the most important things on the earth, but we aren’t. We are really much less important than plants! If all the people on the earth left the planet tomorrow, life would not stop. The plants, animals, and everything else would go on living. But, if all the green plants died, the Earth would become a very different place. The air will change, and neither animals nor people will be able to live in that air. All living things need plants to make the right kind of air. But they also need them for something else — food. Living things need food to grow, but only plants can make their own food. Green plants get light from the sun and water from the ground, and turn it into food. Nothing else can do that!
答案：5. C
