A recent study reports that elementary school students who were given a nutritious breakfast each morning had higher test scores than students who did not recieve the breakfast. For this study, what is the independent variable?
A. the students who were not given the nutritious breakfast
B. the test scores for the students
C. the students who were given the nutritious breakfast
D. whether or not a breakfast was given to the students
D. whether or not a breakfast was given to the students
(this multiple choice question has been scrambled)