Which of the following protocols is used by Windows to securely access a remote computer?

RAS (Remote Access Service) is a Windows feature for establishing dial-up or VPN network connections, not a protocol for graphical remote desktop sessions.

Telnet transmits all data including credentials in plaintext over the network, making it fundamentally insecure and unsuitable for secure remote access.

PPP (Point-to-Point Protocol) is a data link layer encapsulation protocol used for serial and dial-up connections, not for remote desktop or terminal access to a computer.

RDP (Remote Desktop Protocol) operates on TCP port 3389 and is built into Windows to deliver encrypted, full graphical remote desktop sessions. It supports Network Level Authentication (NLA) and TLS encryption, making it the standard secure method for remotely accessing and controlling a Windows computer. No third-party software is required on the server side, as Windows includes the RDP server component natively.