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LeannaChina · 发表于 2011-3-9 19:37:56

Q21:
Which of the following most logically completes the passage?

Mastitis is an infection of the udder in cows that, although not dangerous, causes them to give poor-quality milk.Most cases of mastitis are caused by the bacterium Staphylococcus aureus, against which antibiotics are ineffective.However, a related bacterium, Staphylococcus simulans, quickly clears up even severe infections of S. aureus simply by displacing the bacteria.S. simulans is nevertheless unlikely to become the preferred treatment for cases of mastitis, since ______.

certain dangerous bacteria that normally cannot take hold can do so in the presence of S. simulans
the current resistance of S. aureus to antibiotics derives in part from a past pattern of overuse of those antibiotics
the milk from cows infected with S. aureus is generally not of such poor quality as to be entirely unusable
careful farming practice can reduce the incidence of mastitis to a minimum
the only symptom of mild cases of mastitis is the deterioration in the quality of the milk produced

Answer:

A 是说有S 会有危险的细菌
C 说有S 牛奶就不能喝了。。。。那。。。二者怎么看着都像对呢。。。。

Summer明明 · 发表于 2011-3-9 20:02:11

答案是A吧结论Ss能通过代替Sa消灭Sa，原因肯定跟Ss有关啊。A说Ss同样不能控制，则可能危害比Sa更大。C选项只说Sa的牛奶只是质量差没说Ss的牛奶不能喝啊

LeannaChina · 发表于 2011-3-9 20:23:34

en ,,,C中的unusable 就是不能用的。。。恩。。。

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