Dr Bischer Is Conducting a Study to Determine If Men

Dr. Bischer is conducting a study to determine if men who wear a new type of soccer uniform made from a specially designed fabric will perform better in soccer matches. She recruits a professional soccer team to participate. She randomly assigns half of the men to wear the new-material uniforms made in the color blue and the other half to wear old-material uniforms made in the color red. Although the men know of the uniform test, they are not told which of the uniforms is made from the new material. They are asked to wear their assigned uniforms and score as many goals as possible in a practice scrimmage game against one another. Dr. Bischer is noting the number of goals scored. Ultimately, the men who are wearing the old uniforms score more goals and therefore win the game. Dr. Bischer speculates that the new uniforms are not more beneficial to performance than the old uniforms, but she will rerun her study a few more times.
-What is the independent variable in Dr. Bischer's study?

A) The type of uniform worn-old or new material
B) The number of goals scored
C) The men who did not know their roles in the study
D) Trying to score as many goals as possible