Quisley's Hypothesis Is That Listening to Classical Music Improves Intellectual

Multiple Choice

Quisley's hypothesis is that listening to classical music improves intellectual performance.He randomly divides a mathematics class into two rooms.In room A,music by Mozart plays softly in the background during a lecture.In room B,the students listen to a lecture without background music.The independent variable is ____.

A) whether music played during a lecture.
B) mathematical performance.
C) the level of mathematics taught.
D) present only in the control group.