题目

大田种植转基因抗虫棉的同时，间隔种植少量非转基因的棉花等其他农作物，供棉铃虫取食。这种做法的主要目的是A. 维持棉田物种的多样性 B. 减缓棉铃虫抗性基因频率增加的速度C. 使食虫鸟有虫可食 D. 维持棉田生态系统中的能量流动 答案：【答案】B【解析】转基因技术在农业生产上已经应用，转基因抗虫棉可以有效地防御棉铃虫，减少农药的使用，但也会出现一些环境或生态问题。例如棉铃虫抗性基因频率的增加速度加快等问题。农田种植植物的目的是获得产量高的农作物，人工种植，人工管理，不需要题干抗虫棉与非转基因棉花间隔 简答 阅读短文，根据短文内容回答问题。Mark is a 16-year-old student. He has a very healthy life. However, one year ago, he was not so healthy. From Monday to Friday, he studied every day but hardly did any sports. He often used the Internet. Although his parents asked him to exercise, he never did. He sometimes helped his mother with housework, but only once a week. On weekends, he liked watching TV. Then the bad result came, he became fat and had few friends. One day, the doctor in his school talked with him. He told Mark to do more sports because it was good for his body and mind. From then on, Mark decided to change(改变) his habits. Now, he does sports more often than before, such as playing basketball and soccer. He plays less computer games. After dinner, he often takes a walk with his parents. Doing exercise helps him become healthy and study better. Now he also has more friends.1.Did Mark have a healthy life one year ago?____________________________________________________________________2.How often did Mark help his mother with the housework? ____________________________________________________________________3.What did Mark like doing on weekends?____________________________________________________________________4.How old is Mark?____________________________________________________________________5.What kind of sports does Mark do now? ____________________________________________________________________