Answer:
The number of hours worked per week
Explanation:
To study this issue, one administrator was assigned to examine the relationship between the number of hours worked per week in a semester and that semester's GPA for a random sample of students.
Here the explanatory variable is - the number of hours worked per week.
An explanatory variable or also called an independent variable, is the variable that is manipulated by the researcher based on the variations in the response variable of an experimental study.