A College Professor Gives Surprise Pop-Quizzes to His Students at Different

Multiple Choice

A college professor gives surprise pop-quizzes to his students at different times during the semester.They must make sure they are always prepared because they cannot predict when these quizzes will take place.This type of schedule is a ____.

A) fixed-ratio schedule
B) fixed-interval schedule
C) variable-interval schedule
D) variable-ratio schedule