问题 选择题

“豆粮间作,瓜类和豆类轮作”的种植方式能够提高作物产量,主要原因是该方式(  )

A.通过增加种植密度,抑制杂草生长

B.能够利用植物固氮,提高土壤肥效

C.通过调整害虫的食物链,减少病虫害

D.通过增加单位土地的有效光合面积,提高光能利用率

答案

生物与生物之间的关系常见有:捕食关系、竞争关系、合作关系、寄生、共生关系等.共生是指有些生物与其它生物共同生活在一起,相互依赖,彼此有利,一旦分开,两者都要受到很大影响,甚至不能生活而死亡,这就是共生.根瘤菌生活在豆科植物的根部,它为植物固定空气中的氮气,转变为植物能够吸收的含氮物质,被植物利用;而根瘤菌生活所需要的有机物是植物进行光合作用储存的有机物.因此,“豆粮间作,瓜类和豆类轮作”的种植方式能够提高作物产量,主要原因是豆类的根部有根瘤菌,能够利用植物固氮,提高土壤肥效.

故选:B

完形填空

All our dreams have something to do with our feelings, fears, longings, wishes, needs and memories. But something on the “outside” may affect what we ___1__. If a person is hungry or tired or cold, his dream may include a feeling of this kind. If the ___2___ on your body has slipped off your bed, you may dream that you are ___3___ or resting on the ice and snow. The material for the dream you will ___4___ tonight is probably to come from the experiences you have today.

__5___ the subject of your dream usually comes from something that has an effect on you ___6___ you are sleeping (feeling of cold, a noise, a discomfort, etc.) and it may also use your past experiences and the wishes and interests you have now. This is why very young __7___ are likely to dream of fairies(仙女), older children of school examinations, ___8___ people of food, homesick soldiers of their families and prisoners of freedom.

To show you how that is ___9___ while you are asleep and how your wishes or needs can all be joined together in a dream, ___10___ is the story of an experiment. A man was asleep and the back of his ___11___ was rubbed ___12__ a piece of cotton. He would dream that he ___13___ in a hospital and his girlfriend was visiting him, ___14___ on the bed and feeling gently his hand!

There are some scientists who have made a special ___15__ of why we dream, what we dream and what those dreams ___16__. Their explanation of dreams, though a bit reasonable, is not accepted by everyone, but it ___17__ an interesting approach(方法) to the problem. They believe that dreams are ___18___ expressions of wishes that didn’t ___19___. In other words, a dream is a way of having your wishes ___20___ out.

1. A. long       B. dream C. think   D. wish

2. A. blanket   B. book   C. shoe    D. trousers

3. A. working B. running      C. sleeping     D. studying

4. A. have       B. meet   C. see      D. think

5. A. But B. For     C. Because      D. So

6. A. before    B. while  C. after   D. during

7. A. children  B. fathers       C. drivers       D. gentlemen

8. A. happy     B. sad     C. hungry       D. old

9. A. taking    B. happening  C. dreaming    D. carrying    

10. A. that      B. it C. here    D. this

11. A. leg       B. head   C. body   D. hand  

12. A. in  B. of       C. with    D. off

13. A. left       B. lived   C. gave   D. was

14. A. waiting B. sitting C. smiling      D. speaking

15. A. study    B. watch  C. sleep   D. way

16. A. stand    B. do      C. form   D. mean

17. A. makes   B. offers  C. finds   D. demands

18. A. any      B. almost C. mostly       D. hardly

19. A. get       B. arrive  C. come true   D. believe in

20. A. carried  B. taken  C. kept    D. called

问答题 简答题