Which of the following HTTP methods is idempotent and used to completely replace a resource on the server? 

The HTTP PUT method is idempotent, meaning that making the same request multiple times will result in the same outcome. It is used to completely replace a resource on the server with the provided data. If the resource does not exist, PUT can create it. However, subsequent PUT requests with the same data will not change the state of the resource, ensuring idempotency. Why Other Options are Incorrect: A) GET: The GET method is idempotent but is used to retrieve data, not replace it. B) POST: The POST method is not idempotent, as multiple requests can result in the creation of multiple resources. D) DELETE: While DELETE can be idempotent (deleting the same resource multiple times has no additional effect), it does not replace a resource. E) PATCH: The PATCH method is not idempotent and is used for partial updates to a resource, not complete replacement.