Which command is used to validate Terraform configuration files?

Correct answer: terraform validate

Option A is correct because 'terraform validate' is the official Terraform CLI command that checks whether configuration files in a directory are syntactically valid and internally consistent without accessing any remote services or state. Option B is incorrect because 'terraform check' is not a valid Terraform CLI command and does not exist in the Terraform toolset. Option C is incorrect because 'terraform verify' is also not a recognized Terraform command. Option D is incorrect because 'terraform test' is a separate command introduced in Terraform 1.6 for running module unit and integration tests written in HCL, not for validating configuration syntax.