Dung to Death Fields across Europe are contaminated with dangerous levels of the antibiotics given to farm animals. The drugs, w

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问题                                Dung to Death
Fields across Europe are contaminated with dangerous levels of the antibiotics given to farm animals. The drugs, which are in manure sprayed onto fields as fertilizers, could be getting into our food and water, helping to create a new generation of antibiotic-resistant "superbugs".
The warning comes from a researcher in Switzerland who looked at levels of the drags in farm slurry,(46).
Some 20,000 tons of antibiotics are used in the European Union and the US each year. More than half are given to farm-animals to prevent disease and promote growth.(47)
Most researchers assumed that humans become infected with the resistant strains by eating contaminated meat. But far more of the drugs end up in manure than in meat products, says Stephen Mueller of the Swiss Federal Institute for Environmental Science and Technology in Dubendorf.(48)
With millions of tons of animals manure spread onto fields of crops such as wheat and barley each year, this pathway seems an equally likely route for spreading resistance, he said. The drugs contaminate the crops, which are then eaten.(49)
Mueller is particularly concerned about a group of antibiotics called sulphonamides.(50) His analysis found that Swiss farm manure contains a high percentage of sulphonamides; each hectare of field could be contaminated with up to I kilogram of the drags. This concentration is high enough to trigger the development of resistance among bacteria, But vets are not treating the issue seriously.
There is growing concern at the extent to which drugs, including antibiotics, are polluting the environment. Many drugs given to humans are also excreted unchanged and are not broken down by conventional sewage treatment.

A.  They do not easily degrade or dissolve in water.
B.  And manure contains especially high levels of bugs that are resistant to antibiotics, he says.
C.  Animal antibiotics is still an area to which insufficient attention has been paid.
D.  But recent research has found a direct link between the increased use of these farmyard drugs and the appearance of antibiotic-resistant bugs that infect people.
E.  His findings are particularly shocking because Switzerland is one of the few countries to have banned antibiotics as growth promoters in animal feed.
F.  They could also be leaching into tap water pumped from rocks beneath fertilized fields.

选项

答案A

解析 选项A中的主语They提示我们应该寻找一个复数的先行词,根据句子的意思:……既不衰减又不溶于水,这个they指的不是人而是物,我们在上一句里找到sulphonamides这个复数形式的名词,从意思上看也正合适。
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