Which AdWords feature is most effective for preventing their search ads from appearing at night or on weekends?

The owners of a coffeehouse downtown would like to run an “afternoon espresso” promotion to increase sales during the afternoon hours on weekdays. Which AdWords feature is most effective for preventing their search ads from appearing at night or on weekends? 

A) Managed placements
B) Keyword planner
C) Custom ad scheduling 
D) Automatic bidding