Which of these Terraform commands is used to clean or remove all associated resources of the current directory?

The command that is utilized to clean or remove all associated resources in the current directory is indeed the "terraform destroy" command. This command is pivotal in Terraform as it effectively dismantles the entire infrastructure that was provisioned based on the configuration files present in the current directory. When executed, "terraform destroy" goes through the state file, identifies all the resources that have been created, and proceeds to delete them, thus ensuring that no leftover resources remain in the cloud provider environment.

This command is particularly useful during the lifecycle of infrastructure management, especially in development and testing scenarios where the infrastructure may need to be frequently torn down and rebuilt. It offers a straightforward way to clean up resources and prevent unnecessary charges that might accrue from resources that are no longer in use. By confirming the destruction, the user ensures that they are intentionally removing the infrastructure, thereby adding a layer of safety against accidental deletions.

The other command options mentioned are not valid Terraform commands for this purpose. "terraform clean" and "terraform shutdown" do not exist in the Terraform command set, while "terraform remove" is not designed to handle the complete removal of resources in the comprehensive way that "terraform destroy" does.