Universal Containers wants to use an existing prompt template inside Flow as part of automation.

Comprehensive and Detailed Explanation From Exact Extract:

The Prompt Builder documentation shows that prompt templates can be invoked from Flows using a Flow Action. It describes “Call a prompt template from Flow” and “Flow Core Action: Prompt Template Actions.” While Invocable Apex (option A) could technically trigger templates, the standard, declarative, recommended approach is a Flow Action (option C). “Einstein for Flow” (option B) is not the standard naming used in this context. So option C is correct.