Lin is a network security administrator for a government contractor. The company's wireless local area network $($WLAN$)$ uses Wi$-$Fi Protected Access version $2($WPA$2)$ encryption. The network was hacked recently, and Lin suspects that WPA$2$ encryption was broken by a key reinstallation attack. What action is best to ensure secure connections until stronger encryption can be implemented?

A$.$ Require all users to attend security awareness training.

B$.$ Require users to use a virtual private network $($VPN$)$ on the WLAN.

C$.$ Require users to change their system passwords using strong password guidelines.

D$.$ Install a firewall on user computers.