A company has an issue with field users logging into VPN to connect to the mail server, and leaving their computers connected while in public places. The administrator needs to prevent both unauthorized access to the company email and data, and limit the impact on the VPN server. Which of the following BEST achieves this goal?

A.
Set VPN to disconnect after five minutes of inactivity.

B.
Use registry settings to lock computers after five minutes of inactivity, and limit VPN connections to two hours.

C.
Use group policy to lock computers after five minutes of inactivity, and limit VPN connections to one hour.

D.
Provide web mail access to all users.