[url=]41.[/url][c1] Dental researchers recently discovered that toothbrushes can become contaminated with bacteria that cause pneumonia and strep throat. They found that contamination usually occurs after toothbrushes have been used for four weeks. For that reason, [url=]people[/url] should replace their toothbrushes at least once a month.[c2] Which of the following, if true, would most weaken the conclusion above? (A) The dental researchers could not discover why toothbrush contamination usually occurred [url=]only after [/url][c3] toothbrushes had been used for four weeks. (B) The dental researchers [url=]failed to investigate [/url][c4] contamination of toothbrushes by viruses, yeasts, and other pathogenic microorganisms. (C) The dental researchers found that among people who used toothbrushes contaminated with bacteria that cause pneumonia and strep throat, the incidence of these diseases was[url=] no higher than [/url][c5] among people who used uncontaminated toothbrushes. C [url=](D)[/url][c6] The dental researchers found that people who rinsed their toothbrushes thoroughly in hot water after each use were as likely to have contaminated toothbrushes as were people who only rinsed their toothbrushes hurriedly in cold water after each use. (E) The dental researchers found that, after six weeks of use, greater length of use of a toothbrush did not correlate with a higher number of bacteria [url=]being present.[/url][c7]
[c1]推理链:C通常发生在人们用一支牙刷四周以后 牙刷上的细菌会导致由C引起的病 人们应该至少一个月就换一次牙刷
[c2]主结论
[c3]Support
[c4]无关
[c5]割断因果
[c6]无关
[c7]没有weaken |