题干

某山区实施退耕还林之后,群落经过数十年的演替发展为树林。右图甲、乙、丙分别表示群落演替的三个连续阶段中不同优势植物种群数量变化情况。下列说法中正确的是(   )

A:2阶段的优势植物种群最可能是灌木

B:甲阶段开始时植物种群数量为零,所以此演替为初生演替

C:演替中后一阶段优势物种的兴起,会造成前一阶段优势物种的消亡

D:该过程中,生态系统的恢复力稳定性会逐渐提高

上一题 下一题 0.0难度 选择题 更新时间:2015-07-07 05:56:38

答案(点此获取答案解析)

A

同类题3

根据短文内容, 从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

    Do you still remember the haze(雾霾)in the winter? So many people got terribly ill during or after the haze. ____Here is advice for you to protect yourself in hazy weather.

    Spend less time outdoors.This is the most effective way for self-protection in such bad weather.With PM2.5 increasing 103mg per cubic meter,residents will risk a 2.29% increase of death,which experts found out in 2012.If you have to get out,avoid riding bicycles.____

    Close your windows.Experts advice residents to avoid opening windows at home.If you have to ,avoid the time when smog is at its densest(浓的).____Besides,you can keep plants with broad leaves at home to absorb dust,and use air purifiers(清洁器).

    Smoke less.____In hazy weather,smoking would be even more harmful.Smokers are advised to keep their distance from cigarettes before the weather gets better.

    ____For example ,wear special masks outside to avoid breathing in PM2.5.Then take off your coat after getting indoors and keep it away from your other clean clothes,Don't forget to wash your face,rinse(漱)your mouth,and clean your nasal cavity(鼻腔)to clean the particulate matters(颗粒物)that fall on you.Last but not least,keep off stimulating(刺激性)foods.

A.Wear masks.

B.Pay attention to other daily things.

C.Also avoid rush hours,when pollutants will be denser.

D.That's because haze does harm to the health of people.

E.Cigarettes could cause more particulate matters,which are included in PM2.5 .

F.Take more fruits and vegetables instead,which are good for lung,spleen(脾)and kidney(肾).

G.For residents who use air-conditioner,make sure your apartment has enough oxygen indoors.