Answer: fixed ratio
Explanation:
The fixed ratio schedule in operant conditioning refers to a situation whereby a constant number of responses is involved. The fixed ratio schedules used when an average number of responses have already taken place.
In a fixed schedule, the amount of time is set and unchanging such that the schedule is predictable unlike the variable schedule that changes randomly.
Since Josh visits the store every Sunday, when he is sure she will be there, then he is operating on a fixed schedule in operant conditioning.