http response error code

confuse between a or b.

If an http client receives a 4xx status code from the server, it means that: A. the client can make the same exact request again at a later time, at which point in time it may work B. the client should not make the same request again, as it would yield the same response O C. the client's request was valid, and the requested resource was retrieved successfully D. the server is sending back a nonstandard status code, and the response should be ignored