Universal Containers would like customers to be able to schedule appointments themselves in addition to...

Customer self-scheduling requires an externally exposed booking action, while call-center bookings happen inside Salesforce. The Book Appointment action serves both surfaces.

Option C is correct. The Book Appointment global action returns available appointment slots based on the Scheduling Policy, Work Rules and Operating Hours, and lets a call-center agent confirm one. It is the standard internal-user booking surface.

Option D is correct. The Communities Book Appointment action exposes the same booking capability through an Experience Cloud (Communities) site, enabling customer self-service scheduling without contacting the call center.

Option A is incorrect because Get Candidates returns eligible resources for an existing appointment, not bookable time slots, and is a dispatcher tool.

Option B is incorrect because a nightly optimization job rearranges existing appointments and does not allow customers or agents to choose a slot.