昆嵛山物种丰富多样，能有效控制松毛虫等生物类群的爆发式增长，

搜题请搜索小程序“爱下问搜题”

问题选择题

昆嵛山物种丰富多样，能有效控制松毛虫等生物类群的爆发式增长，这是因为该生态系统（　　）

A．松毛虫的食物来源丰富

B．各种生物之间形成良好的合作关系

C．不适合松毛虫的生存

D．形成了复杂的食物链和食物网

答案

生态系统中各种生物之间吃与被吃的关系构成食物链．生物的种类和数量越多，形成食物链和食物网越复杂，生态系统的自动调节能力越强．昆嵛山物种丰富多样，形成了复杂的食物链和食物网，因此该生态系统的自动调节能力越强，所以昆嵛山物种丰富多样，能有效控制松毛虫等生物类群的爆发式增长．

故选D

解答题

三位数乘两位数，积可能是一个五位数．______．

查看答案

完形填空

完型填空
Robert performs his 24-foot boat past willow(柳树) young trees that stick out of the waters of the Mississippi River. __1__ dances off maples(枫树), their branches heavy with __2__ spring leaves. But a _3__ inspection discloses trouble behind the beautiful sight. Rubbish is __4__ in a logjam(浮木阻塞) and hangs from the tree's branches. For the next three hours Robert and his team pull plastic bags, tanks, bottles and __5__ bowling pins out of the water. Then they __6__ for a picnic table caught in the trees. Welcome to the Mississippi River Beautification Project begun in 1997 with Robert's one man __7__ to pick up rubbish __8__ a 400 mile stretch(伸展) of the 2,340 mile river. That year, often working __9__, the 22-year-old fellow cleaned 150 miles of shoreline. At first the project appeared__10__ and useless. But Robert tried his best to find __11 , and with their backing, he soon had a new boat and five-man __12 -the Boom Crane Crew. Last year alone the crew __13_ from the water 44,055 gallon durms,1,104 tires and enough plastic bags to __14__ a football field. Much of the waste will be __15__. "Robert's operation is the only one actually in __16___on the river," says Mark of the Mississippi River Basin Alliance, a union of environmental groups. "It's the __17_I have ever seen in 20 years, and he is inspiring others to do the __18_ ." "The river has given me a livelihood and brought me so much _19_ ," Robert says, "I want to do something in __20_ ."
( )1. A. Sunlight ( )2. A. ripe ( )3. A. wider ( )4. A. placed ( )5. A. ever ( )6. A. come ( )7. A. work ( )8. A. on ( )9. A. alone ( )10. A. large ( )11. A. supporters ( )12. A. family ( )13. A. came ( )14. A. clean ( )15. A. burned ( )16. A. ending ( )17. A. biggest ( )18. A. deed ( )19. A. time ( )20. A. return	B. Air B. brown B. quicker B. piled B. even B. save B. discovery B. in B. strongly B. happy B. workers B. team B. pulled B. cover B. buried B. progress B. earliest B. favor B. joy B. turn	C. Water C. falling C. closer C. trapped C. nearly C. head C. place C. off C. quietly C. impossible C. engineers C. grade C. pushed C. build C. used C. discussion C. latest C. same C. pride C. pay	D. Moonlight D. fresh D. stricter D. thrown D. merely D. fight D. effort D. along D. fiercely D. possible D. pioneers D. class D. appeared D. spread D. recycled D. common D. luckiest D. good D. waste D. trouble

查看答案