Dr. Jeffries, a cognitive psychologist, conducts an experiment examining the effect of emotion on memory. She provides lists of 20 words to two groups of participants. The emotion group is given a list of words that are very emotional in content (e. g., passion, murder). The neutral group is given a list of words that are neutral in content (e. g., houseplant, desk). Each group studies the words for 3 minutes. Then, after a 5-min distractor task (watching a video about nature), Dr. Jeffries then measures how many words each group is able to remember. Which of the following is the independent variable in Dr. Jeffries’ study?

A) The emotional or neutral word list.
B) The length of the distractor task.
C) The number of words remembered.
D) The number of words on the list.