WPA2 (Wi-Fi Protected Access II) is the correct encryption standard to use for a secure Wi-Fi network because it offers a high level of security and is widely supported by modern devices. 'WEP' is an outdated and insecure encryption standard and should be avoided. 'WPA' was the predecessor to WPA2 and, while more secure than WEP, it is not as secure as WPA2. 'Open network' offers no encryption at all, leaving the network vulnerable to eavesdropping and unauthorized use.