题目

Mr. Baker lived in an old and low house. His wife was blind in both eyes and the two children were very young. All his family often went hungry(挨饿). He had nothing but a small piece of field. One autumn he grew some wheat in his field. He hoped it would do well because all family would depend on it. The whole winter it often snowed. And the next spring the wheat was doing well. Mr. Baker was happy. One day Mr. Baker went to watch his wheat. To his surprise, a lot of crops were eaten up by a horse. He became angry but could not find out whose horse had eaten them. He thought the hor图表示某生态系统中构成食物链的四种生物在一段时间内的相对数量．下列说法正确的是（　　）A.甲个体内的DDT含量最高B.该食物链可表示为甲←丙←乙←丁C.甲是生产者，乙、丙、丁消费者D.该生态系统只有甲、乙、丙、丁四种生物