A newspaper article reported that "Children who routinely compete in vigorous after-school sports on hazy days are three times more likely to get asthma than their non-athletic peers." Of the following, which is the most important additional information that would be useful before making a decision about participation in school sports?

• A.Where was the study conducted?
• B.How many students in the study participated in after-school sports?
• C.What is the baseline risk for getting asthma?
• D.Who funded the study?
• E.None of the above