What is a 'reverse proxy' and how does it improve security compared to exposing the application server directly?

• A.A reverse proxy encrypts data between the client and the application server with its own key pair; it provides load balancing, can enforce a single sign-on session, cache static files, and gives a central point for patch management
• B.A reverse proxy sends client requests from the backend to the internet, hiding the client's IP address; it provides anonymous browsing, can block outbound sites, and gives a central point for URL filtering
• C.A reverse proxy replaces the application firewall on the server, removing the need for patching; it provides database failover, can rewrite SQL queries, and gives a central point for query logging
• D.A reverse proxy forwards client requests to a backend server, hiding the backend server's IP, port, and technology stack; it provides SSL termination, can enforce security headers, absorb DoS traffic, and gives a central point to apply WAF, rate limiting, and request filtering