Anderson Is Reading His Morning Paper and Sees the Following

Multiple Choice

Anderson is reading his morning paper and sees the following headline: "Men Should Avoid Rock Music When Playing Board Games." (This headline is based on a study conducted by Fancourt, Burton, & Williamon, 2016.) In the study, men and women played the game "Operation" when listening to different types of music. Male participants performed worse when listening to AC/DC than when listening to Mozart, but female participants' performance did not differ based on music.
Which of the following is a variable in this study?

A) the sex of the researcher
B) the volume of the music
C) the type of game
D) the sex of the participant