21.GWD21-Q21: Whichof the following most logically completes the passage?
Mastitisis an infection of the udder in cows that, although not dangerous, causes themto give poor-quality milk. Most cases ofmastitis are caused by the bacterium Staphylococcus aureus, againstwhich antibiotics are ineffective. However, a related bacterium, Staphylococcus simulans, quicklyclears up even severe infections of S. aureus simply by displacing thebacteria. S. simulans isnevertheless unlikely to become the preferred treatment for cases of mastitis,since ______. A. certaindangerous bacteria that normally cannot take hold can do so in the presence of S.Simulans B. thecurrent resistance of S. aureus to antibiotics derives in part from apast pattern of overuse of those antibiotics C. themilk from cows infected with S. aureus is generally not of such poorquality as to be entirely unusable
D. carefulfarming practice can reduce the incidence of mastitis to a minimum E. theonly symptom of mild cases of mastitis is the deterioration in the quality ofthe milk produced 答案是A 麻烦翻译一下A吧 我怎么读不懂啊~~~