What is the next step after a client confirms a server's certificate is issued by a trusted CA?

The next step after a client confirms that a server's certificate is issued by a trusted Certificate Authority (CA) is to validate the CA's digital signature on the server certificate using the CA's public key. This step is crucial because it ensures that the certificate has not been tampered with and that it indeed comes from a trusted source. The validation process involves the client using the public key from the trusted CA to verify the digital signature on the server's certificate. If the signature is valid, it confirms both the authenticity of the certificate and that the server can be trusted for secure communication.

Other choices are out of context in this scenario. Matching the domain names is generally an important step in the validation process, but it occurs independently of the trust established by the CA. The generation of the master secret and post-master secret pertains to the encryption of the session rather than the certificate validation process itself.