Consider the Following Statement, "In a Nationwide Study, Children on an All-Organic

Multiple Choice

Consider the following statement, "In a nationwide study, children on an all-organic diet are more alert in school than those not on an all-organic diet." Which of the following is a plausible confounding variable in this study?

A) Parents' social-economic status
B) School start times
C) The quality of the non-organic diet
D) All of these
E) None of these