Which of the following is NOT and valid scan technique with nmap?

Nmap's Window scan (-sW) examines the TCP Window field of RST packets to detect open ports.

Nmap's SYN scan (-sS), also known as a half-open scan, is a common and stealthy port scanning technique.

Nmap's ACK scan (-sA) is used to map firewall rulesets and determine if a port is filtered or unfiltered.

Nmap's Connect() scan (-sT) is a basic TCP scan that completes a full three-way handshake and is equivalent to the system's connect() call.

RST refers to the Reset flag in TCP, which is part of the response packets in various scan types (like FIN scan, Xmas scan, or Null scan responses), but 'RST' itself is not a distinct Nmap scan technique.