If a module declares a variable without a default value, you must pass the value...

Rationale for Correct Answer (True):

Variables without defaults are required inputs. If the calling module doesn’t supply a value, Terraform will fail with an error at plan time.

Analysis of Incorrect Option:

False: Incorrect, because Terraform does not assume defaults when none are provided.

Key Concept:

Terraform modules enforce required vs. optional variables depending on whether a default is set.