The correct answer is: C. Both request and response.
A request field is present in both request and response messages. The request field contains the information that the client is requesting from the server. The response field contains the information that the server is sending back to the client.
Here is an example of a request message:
GET / HTTP/1.1
Host: www.example.com
In this example, the request field is GET / HTTP/1.1. This indicates that the client is requesting the / resource from the server using the HTTP/1.1 protocol.
Here is an example of a response message:
“`
HTTP/1.1 200 OK
Content-Type: text/html
Content-Length: 100
Hello, world!
“`
In this example, the response field is HTTP/1.1 200 OK. This indicates that the server has successfully processed the request and is returning a 200 OK status code. The Content-Type and Content-Length fields indicate the type and length of the response body, which in this case is the text Hello, world!.