Answer:
The correct answer is: Variable Interval.
Explanation:
Variable interval can be understood as a type of schedule used in Operant Conditioning in which a reinforcement is given to the conditioning subject after certain period of time. This period of time changes everytime, is variable so the reinforcers are not always predictable.
In this particular case, Karla is being reinforced using the variable interval schedule because she does not know when the next pop quiz will be.
The correct answer is Variable Interval.