Though sucking zinc lozenges has been promoted as a treatment for the common cold, research has revealed no consistent effect. Recently, however, a zinc gel applied nasally has been shown to greatly reduce the duration of colds. Since the gel contains zinc in the same form and concentration as the lozenges, the greater effectiveness of the gel must be due to the fact that cold viruses tend to concentrate in the nose, not the mouth.
In order to evaluate the argument, it would be most helpful to determine which of the following?
题干分析
题目: 1. 研究发现, 口服Zn没有持续效果; 2. 鼻腔用Zn有持续效果; 3. 口服的和鼻用的含有的Zn一样
结论: 鼻用Zn有持续效果的原因是因为病毒集中在鼻子而不是在口腔
A. Zn是否只对感冒有效.....题目讨论的是鼻子和嘴, 无关
B. 不含Zn的药物, 口服的效果...这个没有涉及到鼻子, 无关
C. 频繁感冒是否是Zn缺乏...不影响结论, 无关
E. 对重感冒是否有效, 不影响结论, 而且没有涉及嘴, 无关
D. 正确。是否含有其他成份影响Zn的活性.
如果是, 则gel的持久效果可能是因为其他成份导致Zn活性增强, 而不是用药于鼻腔的缘故, 削弱结论
如果否, 则属于排除他因, 说明两种药物没有别的差别, 很可能是用药部位导致疗效差别, 加强结论