题干

下图为碳循环示意图,下列叙述正确的是     

A:图中由生产者、II、III和IV构成的食物链中,能量流动是单向、逐级递减的

B:生产者为第一营养级,①②⑥⑧之和为生产者固定的总能量

C:①⑦⑧过程以CO2的形式进行,②③④⑤⑥过程以有机物的形式进行

D:根瘤菌与豆科植物互利共生时,其生命活动所需的有机碳来自于⑥过程

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答案(点此获取答案解析)

C

同类题2

根据短文理解,选择正确答案。

    Coffee drink is widespread. When people argue about whether coffee is good for health, they're usually thinking of the health of the coffee drinker. Is it good for your heart? Does it increase blood pressure? Does it help you concentrate? However, coffee affects the health of the human population in other ways, too.

    Traditionally, coffee bushes were planted under the shade of taller trees. However, more and more farmers in Latin America are deforesting the land to grow full sun coffees. At first, this increases production because more coffee bushes can be planted if there aren't any trees. With increased production come increased profits.

    Unfortunately, deforesting for coffee production immediately decreases the local wildlife habitat, because native birds nest and hide from predators(捕食者)in the tall trees and migrating birds rest there.

    Furthermore, in the long term, the full-sun method also damages the ecosystem because more chemical fertilizers and pesticides(杀虫剂)are needed to grow the coffee. The fertilizers and pesticides kill insects that eat coffee plant, and then the birds eat the poisoned insects and also die. The chemicals kill or sicken other animals as well, and can even enter the water that people will eventually drink.

    Fortunately, farmers in Central and South America are beginning to grow more coffee bushes in the shade. We can support these farmers by buying coffee with such labels as "shade-grown" and "bird-friendly".

    Sure, these varieties might cost a little more. But we're paying for the health of the birds, the land, ourselves, and the planet. I think it's worth it.