问题
选择题
下面几种生物构成的一条食物链的起点是（ ）
A．青草
B．鹰
C．鸡
D．虫
答案
食物链和食物网是生态系统的营养结构，它表示的是生产者和消费者之间的食物联系．
食物链的写法是：起点是生产者，依次是初级消费者→次级消费者→三级消费者→…终点是最高级别的消费者，中间用箭头连接，箭头总是指向捕食者．综上所述B、C、D选项错误，只有A选项正确．
故选：A．
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下面几种生物构成的一条食物链的起点是（ ）
A．青草
B．鹰
C．鸡
D．虫
食物链和食物网是生态系统的营养结构，它表示的是生产者和消费者之间的食物联系．
食物链的写法是：起点是生产者，依次是初级消费者→次级消费者→三级消费者→…终点是最高级别的消费者，中间用箭头连接，箭头总是指向捕食者．综上所述B、C、D选项错误，只有A选项正确．
故选：A．
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| In America, on school and work days, breakfast in most homes is often a hurried meal of milk, bread, juice or coffee. Some people even don't have it in order to get to 1 or school on time. Others just stop at coffee shops for coffee. But on weekends, 2 are quite different. People usually get up late, so they have enough time to have a large breakfast with eggs, home-fried potatoes and bread. Lunch is just a 3 break from the day's work rather than a large,long meal. It usually lasts 4 half an hour or an hour, so family members do not have time to 5 home. Most people have a sandwich or a hamburger, and fruit or ice cream for lunch. 6 people either take their lunches to work in the brown paper "lunch bag", 7 eat a sandwich at a fast-food restaurant. Children 8 to bring the "lunch box". Dinner is the most 9 meal of the day in the United States. At this meal, most American families can sit down 10 . It is usually a hot, large meal and it is quite different from lunch, which is often cold and quick. 11 usually cooked dinner for their families in the past. Nowadays, 12 , with more women working and as a result of "women's liberation (解放)", men are doing more in the 13 . Dinners throughout America are quite 14 , but most people have a meat djsh, a vegetable,and rice or bread. Milk, water and soft drinks are common at dinner, but wine is only for 15 occasions (场合). Dinner is usually eaten between 5:00 p. m. and 7:00 p. m. and often in restaurants. Most Americans enjoy themselves at this time. | ||||
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