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

The command that is used to clean or remove all associated resources defined in the current Terraform configuration is indeed the command to destroy those resources. The terraform destroy command effectively deletes all resources that are part of the current Terraform state file, which corresponds to the configuration in the directory you're working in. This is especially useful when you want to tear down your entire infrastructure stack neatly and ensure that there are no lingering resources consuming costs or affecting your environment.

The other options do not exist or do not serve the purpose of removing resources. "terraform clean" is not a recognized command in Terraform; there is no cleanup command specifically intended for this function. "terraform remove" is also not a valid command. Additionally, "terraform shutdown" does not exist as a command within Terraform, making it impossible to use for resource management. Thus, the choice to use terraform destroy to remove all associated resources is the only accurate option available.