TLS (Transport Layer Security) certificates are validated by browsers to ensure secure communication. Browsers maintain a trusted store ofpublic keysfrom known Certifying Authorities (CAs), which are used to verify the digital signature of a TLS certificate presented by a server. This process involves checking the certificate’s signature against the CA’s public key to confirm its authenticity and validity. If the signature matches and other criteria (e.g., expiration, revocation) are met, the certificate is deemed valid.

Option A ("The browser contains the private key..."): Incorrect, as browsers do not contain private keys of CAs; private keys are kept secret by the CAs themselves.

Option B ("The browser contains the public key..."): Correct, as browsers use CA publickeys to validate certificates, enabling differentiation between valid and invalid TLS certificates.

Option C ("The browser contains both the public and private key..."): Incorrect, as browsers only store public keys, not private keys, for security reasons.

Option D ("The browser does not have any mechanism..."): Incorrect, as browsers have robust mechanisms (via CA public keys) to validate TLS certificates.

The correct answer is B, aligning with the CAP syllabus under "Secure Communication" and "TLS Configuration."References: SecOps Group CAP Documents - "TLS/SSL Security," "Certificate Validation," and "OWASP Cryptographic Practices" sections.