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 nasaly 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 due to the fact that cold virus 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:
A. wheter zinc is effective only against colds, or also has an effect on other virally caused diesases.
B. wheter there are remidies that do not contain zinc but that, when taken orally, can reduce the duration of colds
C. whether people who frequently catch colds have a zind deficiency.
D. whether either the zinc gel or the lozenges contain ingredients that have an impact on the activity of the zinc.
E. whehter the zinc gel has an effect on the severity of cold symptoms, as well as their durations.
答案给的是E， 我选D，想不明白， 请NN指点
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