In Melody's Class, She Takes Attendance on Average Every Five

Multiple Choice

In Melody's class, she takes attendance on average every five to ten days, and students who are present receive extra points. Sometimes she will take attendance two or three days in a row, but she never lets the students know when this will happen. This is an example of what type of reinforcement schedule?

A) Fixed-interval
B) Fixed-ratio
C) Variable-interval
D) Variable-ratio