Parent modules can always access a child module’s variable values.

The correct answer is B because Terraform modules have clear input and output boundaries. A child module’s input variables are scoped to that child module and are not automatically exposed back to the parent module. The parent module can pass values into a child module by setting arguments in the module block, but it cannot directly access the child module’s variable namespace. Terraform does not support references such as module.child.var.example. When a child module needs to share information with its caller, the child module must define output values. The parent module can then reference those outputs using syntax such as module.child.output_name. This module interface keeps configurations reusable, predictable, and encapsulated, which is a core Terraform module design principle.