Researchers wanted to investigate whether babies have a sense of right and wrong. They showed each of 60 babies a puppet show in which a red puppet was trying to open a heavy box lid. A second puppet, called the helper, would try to help the red puppet open the box, while a third puppet, called the hinderer, would try to slam the box lid down. After watching the show, each baby was presented with a tray containing the helper puppet and the hinderer puppet, and the researcher recorded which puppet the baby reached for. The researchers wanted to determine whether the babies would reach for the helper pupped more than for the hinderer puppet. As part of the show, a green puppet and a yellow puppet served as the helper and hinderer. For each baby, a coin was tossed to determine which color would serve which role. Which of the following is the most important reason for the random assignment of color to role in the study?

(A)Slamming the lid might cause wear on the hinderer puppet after 60 shows. The random assignment of color to role permits more even wear between the helper and the hinderer.

(B) The puppeteer might grow tired of doing the same show with the same puppet colors. The random assignment of color to role keeps the show fresh for each performance.

(C) If the same role is played by the same color puppet, the babies might show a preference for the color instead of a preference for the role.

(D)The random assignment of color to role allows the researchers to determine if one color is better than another for teaching babies right from wrong.

(E) Boys and girls might prefer different colors. The random assignment of color to role ensures that the show is equally accessible to boys and girls.