Users are issued security tokens to be used in combination with a PIN to access the corporate virtual private network (VPN). Regarding the PIN, what is the MOST important rule to be included in a security policy? 
A、Users should not leave tokens where they could be stolen 
B、Users must never keep the token in the same bag as their laptop computer 
C、Users should select a PIN that is completely random, with no repeating digits 
D、Users should never write down their PIN