$40.$ We cannot use the IEEE $802\mathrm{.}1$X standard in wireless LANs for authentication because

O a$.$ the gateway to the network is a wireless access point.

O b$.$ wireless clients cannot work with a central authentication server.

O c$.$ border firewalls drop incoming traffic from wireless clients.

$$ d$.$ the $802\mathrm{.}1$X standard implicitly assumes that the connection between a supplicant and an authenticator is secure$.$