下图为某生态系统中黄杉的三个种群龄级（以胸径的大小表示）的取样调查图。其中种群A为自然状态，种群B、C受到了不同强度的人为干扰。据图得出的结论正确的是（）
A.人为干扰对B、C种群各龄级的数量没有显著影响
B.种群A中低龄级黄杉个体数量大于种群B
C.种群B中高龄级的黄杉被采伐有利于低龄级黄杉的生长
D.种群C中高龄级黄杉数量锐减，导致其垂直结构的层次简单
参考答案：C
解析：由图可知B、C在受到人为干扰后B中龄级比自然的多，而C中各龄级都比自然的少，故A错误。种群中低龄级比个体数量小于B种群，故B错误。种群B中高龄级的黄杉被采伐后低龄级的黄衫能接触到充分的光照，有利于其生长，故C正确。种群数量减少群落的结构在短时间内不一定会发生改变，故D错误。考点：本题考查种群与群落相关知识，意在考察考生对知识点的理解掌握和对图形分析能力。
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| How 1 do you know about manners (礼仪)? Different countries have 2 manners. In 3 Asian countries, it is good manners to take off your shoes before you go into a house. 4 in European (欧洲) countries, even if they sometimes become very dirty, this is not done. If you are a 5 in a Chinese house, when you have a meal, you usually do not 6 the food. You often leave a little to 7 that you have had enough. But in England, a visitor always finishes food to show that he has 8 it. We must know the customs (风俗) of other 9 so that they will not think 10 bad-manners. People all over the world 11 that a well-mannered person should be kind and 12 to others. If you remember this, at 13 you will not go very far wrong. 14 likes a person with good manners, but no one likes a person 15 bad manners. Keep your manners. |
| ( )1. A. well ( )2. A. same ( )3. A. some ( )4. A. And ( )5. A. stranger ( )6. A. need ( )7. A. say ( )8. A. finished ( )9. A. countries ( )10. A. them ( )11. A. find ( )12. A. careful ( )13. A. end ( )14. A. Somebody ( )15. A. with | B. \ B. different B. any B. So B. traveller B. finish B. see B. enjoyed B. villages B. me B. know B. helpful B. first B. Anybody B. had | C. much | D. many D. interesting D. few D. Or D. foreigner D. have D. show D. drunk D. places D. him D. agree D. healthy D. last D. Everybody D. is |