What command is used to apply changes in Terraform?

The command used to apply changes in Terraform is "terraform apply." This command is fundamental to the Terraform workflow, as it takes the configurations defined in your Terraform files and makes the necessary changes to the infrastructure.

When this command is executed, Terraform first generates an execution plan, which details the actions that will be taken to achieve the desired state defined in your configuration files. It then prompts the user for confirmation before applying the changes. This two-step process allows users to review modifications before they are committed, helping to prevent unintended changes to infrastructure.

The other options do not correspond to any valid Terraform commands used for applying changes. "terraform execute," "terraform start," and "terraform provision" do not exist as standard commands within the Terraform CLI, which further highlights why "terraform apply" is the correct choice for this question.