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?

• AWhether zinc is effective only against colds, or also has an effect on other virally caused diseases  
• BWhether there are remedies that do not contain zinc but that, when taken orally, can reduce the duration of colds  
• CWhether people who frequently catch colds have a zinc deficiency  
• DWhether either the zinc gel or the lozenges contain ingredients that have an impact on the activity of the zinc  
• EWhether the zinc gel has an effect on the severity of cold symptoms, as well as on their duration