Given the advanced techniques for scaling push notifications with OneSignal, identify which scenarios effectively employ these techniques:
- Scenario A: An event planning app sends notifications about local events, but only to users who are currently in the vicinity of the event location.
- Scenario B: A travel app sends the same weekly notification about new travel deals to all users, regardless of their past travel bookings or preferences.
- Scenario C: A fitness app uses machine learning to determine the best time to send workout reminders, based on when individual users are most active in the app.
- Scenario D: A retail app sends notifications featuring products with rich media images to users who have viewed similar products in the app.
Select the scenarios that demonstrate effective use of advanced techniques for scaling push notifications.