题目

All living things on the earth need other living things to live on. Nothing lives alone. Most animals must live in a group, and even a plant grows close together with others of the same kind. Sometimes one living thing kills another, one eats and the __①__    is eaten. Each kind of life eats another kind of life in order to live, and together they form a food chains(链子). Some food chains are simple, while others are not. But all food chains begin with the sun, ② and all food chains become broken up if one of the links(连接) disappears. All life needs sunlight to live on. 位于我国著名重工业基地的高速公路（ ）A．沈阳--大连B．北京--上海C．广州--深圳D．济南--青岛