A module can declare a variable with a default value without requiring the caller to define it. This allows the module to provide a sensible default behavior that can be customized by the caller if needed. References =
[Module Variables]

To see all the resources that Terraform will delete, you can use either of these two commands:
* terraform destroy will show the plan of destruction and ask for your confirmation before proceeding.
You can cancel the command if you do not want to destroy the resources.
* terraform plan -destroy will show the plan of destruction without asking for confirmation. You can use this command to review the changes before running terraform destroy. References = : Destroy Infrastructure : Plan Command: Options

When running a terraform apply -refresh-only, Terraform does not reference the configuration files, but only the state file, credentials, and cloud provider. The purpose of this command is to update the state file with the current status of the real resources, without making any changes to them1.

* A Terraformbackenddetermineswhere and how Terraform state is stored.
* Bothterraform applyandterraform destroyinteract with state, so Terraform needs access to the backend for state storage and updates.
* D (Neither are correct)is incorrect becauseTerraform state is required for both apply and destroy operations.
Official Terraform Documentation Reference:
Terraform Backends

The terraform fmt command is used to rewrite Terraform configuration files to a canonical format and style.
This command applies a subset of the Terraform language style conventions, along with other minor adjustments for readability. Running this command on your configuration files before committing them to source control can help ensure consistency of style between different Terraform codebases, and can also make diffs easier to read. You can also use the -check and -diff options to check if the files are formatted and display the formatting changes respectively2. Running the terraform fmt command during the code linting phase of your CI/CD process can help automate this process and enforce the formatting standards for your team. References = [Command: fmt]2