某种植玉米的农场，其收获的玉米子粒即作为鸡的饲料，也可作为人的粮食，玉米的秸秆则加工成饲料喂牛，生产的牛和鸡供人食用。人、牛、鸡的粪便经过沼气池发酵产生的沼气作为能源，沼渣、沼液作为种植玉米的肥料。关于该人工生态系统，下列说法错误的是（）
A.牛与鸡之间无竞争关系，因为它们所需食物资源不同
B.人与鸡的种间关系是捕食与竞争，人和牛的种间关系是捕食
C.该生态系统实现了能量的循环利用，提高了能量利用率
D.流经该生态系统的总能量来自生产者所固定的太阳能
参考答案：C
读下面一篇文章，根据文中信息完成所给表格，每空不超过三个单词。 People in the United States honor their parents with two special days: Mother’s Day, on the second Sunday in May, and Father’s Day, on the third Sunday in June. These days are set aside to show love and respect for parents. They raise their children and educate them to be responsible citizens. They give love and care. These two days offer a chance to think about the changing roles of mothers and fathers. More mothers now work outside the home. More fathers must help with child-care. These two special days are celebrated in many different ways. On Mother’s Day people wear carnations. A. red one stands for a living mother. A. white one shows that the mother is dead. Many people attend religious services（宗教仪式）to honor parents. It is also a day when people whose parents are dead visit their graves. On these days, families get together at home and in restaurants. They often have outdoor BBQs for Father’s Day. These are days of fun and good feelings and memories. Another tradition is to give cards and gifts. Children make them in school. Many people make their own presents. These are valued more than the ones bought in stores. It is not the value of the gift that is important, but it is “the thought that counts”. Greeting card stores, florists, candy makers, bakeries, telephones companies and other stores do a lot of business during these holidays. 1.
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