Can end users be forced to authenticate by using client certificates and username password credentials?

Can end users be forced to authenticate by using client certificates and username password
credentials?

A.
yes, but by manually changing the parameters is password warning to true in the $
PWDIR/conf/ objects_5_0.c file, to allow for LDAP

B.
No, R71 only supports authentication by client certificates

C.
Yes by editing the protection-level settings

D.
SSL VPN supports server certificates

Explanation: