In a Study on Sleep Habits, It Was Found That

In a study on sleep habits, it was found that college students who got at least 7 hours of sleep the night before a test performed better on exams than college students who got less than 7 hours of sleep.
-Identify the explanatory and response variables in this study.

A) The explanatory variable is exam score, and the response variable is whether a student got at least 7 hours of sleep.
B) The explanatory variable is whether a student got at least 7 hours of sleep, and the response variable is exam score.
C) The explanatory variable is sleep habits, and the response variable is performing better on exams.
D) The explanatory variable is performing better on exams, and the response variable is sleep habits.