Which of the following is NOT an element required in an HTTP request?

In HTTP requests, the essential components include the method, URL, and, in certain cases, a body. The method specifies the action to be performed (like GET, POST, etc.), while the URL indicates the location of the resource on the server. In scenarios where data is transmitted (such as with POST requests), a body might be included to carry the actual content being sent to the server.

The protocol itself, while an essential part of the full request format (including headers and syntax), does not stand alone as an individual component explicitly required in the HTTP request line. The request line will often imply the protocol through its structure—HTTP/1.1 or HTTP/2 for example—but it does not appear as a discrete element in the request. Thus, while the protocol is critical to ensure communication happens properly, it is not one of the explicit parts of the HTTP request that the server requires to process the request.