一块农田中有豌豆、杂草、田鼠和土壤微生物等生物，其中属于竞争关系的是（）
A.田鼠和杂草
B.豌豆和杂草
C.豌豆和其根中的根瘤菌
D.细菌和其细胞内的噬菌体
参考答案：B
解析：田鼠和杂草的关系是捕食，故A错误；豌豆和杂草可以争夺阳光和土壤中的营养物质，故B正确；豌豆和根中的根瘤菌的关系是互利共生，故C错误；细菌和其细胞内的噬菌体的关系是寄生，故D错误。考点：本题考查种间关系的有关知识，意在考查考生理解所学知识的要点，把握知识间的内在联系的能力。
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of the People's Republic of China, the Ministry of Education released (发布) its "Sunny Sports long-distance winter run" program (阳光体育冬季长跑). From October to April, Chinese students have to be 1______ to run a certain distance every day. The 2______ distance for elementary students is 1,000 meters a day, 1,500 meters for middle school students, and 2,000 meters for high school and college students. Some people think that such an 3______ activity will do good to Chinese students. For one thing, it lifts the spirit and builds confidence. For another, it helps you learn new things and remember old information better. More importantly, it is a good idea to develop and improve the 4______ of education. However, other people like parents 5______ the time and energy that it takes the students to work on their academic performances (学业情况) and physical activities. It is obvious that there are more advantages of taking exercise than its disadvantages. Don't be a couch potato! Get out there and run. |