下列属于生态系统的是（ ）
A．一只大象
B．一群飞鸟
C．一片树林
D．一朵云彩
生态系统就是在一定的地域内，生物与环境构成的统一的整体．生物与环境是不可分割的，只有生物不叫生态系统，只有环境也不叫生态系统．其中生物包括植物是生产者，动物是消费者，细菌真菌是分解者．
A、B、一只大象和一群飞鸟都只是部分生物，没有环境，不能构成一个完整的生态系统．不符合题意．
C、一片树林即包括了树林的所有生物，也包括了生物所生存的环境，符合生态系统的概念，是一个生态系统，符合题意．
D、一朵云彩不是生物与环境构成的统一整体，不是一个生态系统，不符合题意．
故选：C
| 完形填空。 | |||
| Farley worked for the Canadian government. One day, he was __1__ to learn more about wolves. Do wolves kill lots of caribou, Do they kill people? They gave him lots of food and clothes and guns. Then they put him on a plane and took him to __2__. The plane put him down and went away. There were no houses or people in this place. But there were lots of animals and lots of wolves. People tell terrible stories about wolves.They say wolves like to kill and eat people.Farley remembered these stories, and he was __3__. He had his gun with him__4 _ . Then one day, he saw a group of wolves. There was a mother wolf with four baby wolves. A father wolf and another young wolf lived with them. Farley watched these wolves every day. The mother was a very __5__ mother. She gave milk to her babies. She gave them lessons about life. They learned how to __6__ food. The father wolf got food for the mother. The young wolf __7__ the children. They were a nice, happy family-wolf family! Farley did not need his __8__ any more. In a short time, he got on well with the family. Farley watched them for five months. He learned that many stories about the wolves were __9__. Wolves do not eat people, and they do not eat many large animals. And he also learned bad things about men. It was men who killed many caribou and wolves. Later, Farley wrote a book about wolves. He wanted people to __10__ them and not to kill them. | |||
| ( )1. A. seen ( )2. A. a small town ( )3. A. afraid ( )4. A. at times ( )5. A. bad ( )6. A. cook ( )7. A. shouted at ( )8. A. food ( )9. A. not good ( )10. A. grow | B. told B. a big city B. happy B. all the time B. good B. make B. looked into B. clothes B. not true B. have | C. heard C. a far place C. angry C. once a week C. hungry C. get C. laughed at C. gun C. not easy C. teach | D. found D. a lonely village D. tired D. every afternoon D. thirsty D. pick D. played with D. plane D. not clear D. understand |