题干

通过下列实验操作和现象能得出相应结论的是(   )

实验操作

现象

结论

A

向收集满CO2的软塑料瓶中加入约1/3体积滴有石蕊试液的水,旋紧瓶盖,振荡

塑料瓶变瘪,溶液变红

CO2能与石蕊反应

B

往久置于空气中的氢氧化钠溶液滴加稀硫酸

有气泡

氢氧化钠溶液已变质

C

在某无色溶液中滴加氯化钡溶液

有白色沉淀

无色溶液中一定含有

SO42-离子

D

把质量相同的镁条与锌粒同时放入相同浓度和体积的盐酸中

镁条与盐酸产生气体更快

镁的金属活动性比锌强

A:A   

B:B   

C:C   

D:D

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答案(点此获取答案解析)

B

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    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.