A certificate authority needs to post information about expired certificates.

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 This prevents clients from trustingcompromised or outdated certificates.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.