You want to create a string that combines a generated random_id and a variable and...

Rationale for Correct Answer: A local value (locals { ... }) is the simplest way to define a reusable expression once and reference it many times via local.. This is exactly what locals are for: reducing repetition and improving readability when combining values like random_id results and variables.

Analysis of Incorrect Options (Distractors):

A (Module): Overkill—modules are for packaging reusable groups of resources, not simple string reuse inside the same configuration.

B (Output value): Outputs are for exposing values to the CLI or to parent modules, not for internal reuse within the same module.

D (Data source): Data sources read existing remote objects; they are not intended for composing local strings.

Key Concept: Using locals to avoid repeating expressions.