Which of the following is the successor of SSL?

GRE (Generic Routing Encapsulation) is a tunneling protocol used to encapsulate network-layer packets inside IP tunnels and has no relationship to SSL or transport-layer security.

IPSec is a network-layer security suite used to encrypt and authenticate IP packets; it operates independently of SSL and TLS and serves a different layer in the protocol stack.

RSA is an asymmetric encryption and key-exchange algorithm used within TLS handshakes as a component, not a protocol that succeeded SSL.

TLS was introduced as the successor to SSL 3.0, first standardized as TLS 1.0 in RFC 2246 (1999) and most recently updated to TLS 1.3 in RFC 8446 (2018). All versions of SSL are now considered deprecated and insecure, and modern secure communications use TLS exclusively. Although the term 'SSL certificate' is still used colloquially, the underlying protocol in all current deployments is TLS.