ACertificate Revocation List (CRL)is adigitally signed list maintained by a Certificate Authority (CA)that containsrevoked or expired certificates. This prevents clients from trustingcompromised or outdated certificates. TPM (A)is a hardware security module, unrelated to certificate revocation. PKI (C)is the overall system managing digital certificates, but it does not store revocation lists. CSR (D)is a request to obtain a certificate, not to revoke one. Reference:CompTIA Security+ SY0-701 Official Study Guide, Security Architecture domain.