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标题: GMAT-21-21请教求解思路 [打印本页]

作者: sv2000 时间: 2005-11-11 14:25
标题: GMAT-21-21请教求解思路

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

作者: yangsh 时间: 2005-11-11 16:12
A, 用这个东西，会导致某些有害病菌take hold.

作者: williamweizh 时间: 2005-11-12 04:45

certain dangerous bacteria that normally cannot take hold can do so in the presence of S. simulans.

这句话意思看不太懂,谁能解释一下?

作者: steveyangxt 时间: 2005-12-18 08:32
有些正常情况下不会出现的细菌在有这种S. simulans.的情况下也能在牛乳房上生长。

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