When generating a request for a new x.509 certificate for securing a website, which of the following is the MOST appropriate hashing algorithm?

RC4 is a symmetric stream cipher used for encryption, not a hashing algorithm, and has been deprecated due to serious cryptographic vulnerabilities making it entirely unsuitable for certificate generation.

MD5 is a hashing algorithm but has been cryptographically broken due to known collision attacks, and the CA/Browser Forum has prohibited its use in certificate signing since it can be exploited to forge certificates.

HMAC (Hash-based Message Authentication Code) is a message authentication mechanism that uses a shared secret key combined with a hash function, making it unsuitable for public-key certificate generation where asymmetric signing is required.

SHA (specifically modern variants like SHA-256 or SHA-384) is the industry-standard hashing algorithm used in X.509 certificate generation and TLS/SSL. It produces a cryptographic digest of the certificate data that is signed by the CA, and modern browsers and standards bodies (NIST, CA/Browser Forum) mandate SHA-2 family algorithms for certificate signatures due to their collision resistance and security strength.