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【单选题】

Most shoppers know the feeling. You stand in front of piles of organic produce and wonder what those premium prices are buying you over and above what you get from standard foods. Not a lot nutrition-wise, it seems. Organic farming may not even be more sustainable. But could the whole debate about organic versus non-organic be missing the point
Understanding nutrition is, of course, vital when it comes to choosing food. In a report published recently, a team from the London School of Hygiene & Tropical Medicine examined 162 papers that compared organic and conventionally-produced food. They concluded that there was no evidence to back up claims that organic food is more nutritious.
But this is only one of the aspects of organic food that shoppers care about, and things get even more complicated when other factors are brought into the equation. Many buy organic fruit and vegetables because they are not sprayed with pesticides. We know these can cause birth defects, cancer, and even the diabetes epidemic but it remains unclear whether the amounts in conventionally-grown fruit and vegetables are high enough to be a health hazard.
And then there are issues unrelated to health. Take energy use. True, some organic farming systems are more energy-efficient, partly because they do not use synthetic fertilisers, which are energy-intensive to produce. However, there is limited pressure on organic farmers to cut emissions. They don’t yet have to do so to qualify for organic status. As Laurie Drinkwater, an expert in sustainable agriculture at Cornell University in New York, points out, "Organic agriculture is not without environmental consequences." Indeed, according to Jules Pretty, an agricultural scientist at the University of Es in Colchester, some organic farms keep weeds down with propane burners (丙烷加热器), which produce carbon dioxide.
Soil erosion is another confounding factor. Many organic farms emphasise crop rotation, in part to ensure that fields are not left uncovered and vulnerable to erosion. The trouble is some organic farmers actually cause erosion by tilling the soil frequently to tackle the weeds.
It’s not about whether organic food is good or a sham. That’s the wrong question. We should be asking how we can make all of agriculture more sustainable. Rather than compare organic and conventional systems in a simplistic way, Drinkwater and Pretty say we should identify the things we want from farms and then design a farming system—organic or otherwise—that best meets those goals.
Producing enough food is an obvious aim, but farmers can also help boost biodiversity, keep rivers free of certain kinds of pollution, and fight climate change. There is also the question of animal welfare. You would probably end up with a system that borrows techniques from many existing farming methods. That would be good news for farmers and the rest of society, even though it might not produce so many snappy headlines. Many people choose organic foods for the reason that ______.

A.
they are approved by many experts
B.
C. they won’t cause diseases
C.
B. they taste better than standard foods
D.
they are free from pesticides
题目标签:热器加热器丙烷
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【单选题】Most shoppers know the feeling. You stand in front of piles of organic produce and wonder what those premium prices are buying you over and above what you get from standard foods. Not a lot nutrition-...

A.
do not use naturally produced fertilisers
B.
produce carbon dioxide when removing weeds
C.
use high doses of weed-killer
D.
use too many resources to qualify for organic status

【单选题】以2-氯丙烷为主要原料制1,2-丙二醇[CH3CH(OH)CH2OH]时,依次涉及的反应类型有 [ ]

A.
加成反应→消去反应→取代反应
B.
消去反应→加成反应→取代反应
C.
消去反应→取代反应→加成反应
D.
取代反应→加成反应→消去反应

【单选题】下列有关热水加热器的说法不正确的是()。

A.
主要用于对供入洗消帐篷内的水进行加热
B.
每次使用完毕,擦拭热水罐外部及燃油过滤器
C.
每6个月擦拭泵内过滤器和用酸性不含树脂的润滑油擦拭燃烧器马达
D.
每使用300次点火器喷嘴后,检查是否积碳,并擦拭干净

【多选题】⾼压加热器分为()

A.
混合式
B.
表⾯式
C.
对流式
D.
逆流式

【单选题】前脱丙烷流程的优点是()。

A.
工艺技术较为成熟
B.
流程复杂
C.
冷量利用比较合理
D.
投资较大

【单选题】不能造成脱丙烷塔压力突升的是()。

A.
晃电
B.
脱丙烷塔回流泵停
C.
脱丙烷塔空冷除盐水泵停
D.
装置仪表风停
相关题目:
【单选题】Most shoppers know the feeling. You stand in front of piles of organic produce and wonder what those premium prices are buying you over and above what you get from standard foods. Not a lot nutrition-...
A.
do not use naturally produced fertilisers
B.
produce carbon dioxide when removing weeds
C.
use high doses of weed-killer
D.
use too many resources to qualify for organic status
【单选题】以2-氯丙烷为主要原料制1,2-丙二醇[CH3CH(OH)CH2OH]时,依次涉及的反应类型有 [ ]
A.
加成反应→消去反应→取代反应
B.
消去反应→加成反应→取代反应
C.
消去反应→取代反应→加成反应
D.
取代反应→加成反应→消去反应
【单选题】下列有关热水加热器的说法不正确的是()。
A.
主要用于对供入洗消帐篷内的水进行加热
B.
每次使用完毕,擦拭热水罐外部及燃油过滤器
C.
每6个月擦拭泵内过滤器和用酸性不含树脂的润滑油擦拭燃烧器马达
D.
每使用300次点火器喷嘴后,检查是否积碳,并擦拭干净
【多选题】⾼压加热器分为()
A.
混合式
B.
表⾯式
C.
对流式
D.
逆流式
【单选题】双酸A和环氧氯丙烷作用后的产物是( )。
A.
聚碳酸酯
B.
顺丁橡胶
C.
尼龙66
D.
环氧树脂
【单选题】前脱丙烷流程的优点是()。
A.
工艺技术较为成熟
B.
流程复杂
C.
冷量利用比较合理
D.
投资较大
【单选题】不能造成脱丙烷塔压力突升的是()。
A.
晃电
B.
脱丙烷塔回流泵停
C.
脱丙烷塔空冷除盐水泵停
D.
装置仪表风停