Which setting provides the best security for a WLAN and authenticates users against a centralized directory store?

Which setting provides the best security for a WLAN and authenticates users against a centralized directory store?
A . WPA2 AES-CCMP and 801.X authentication
B . WPA2 AES-CCMP and PSK authentication
C . WPA2 TKIP and PSK authentication
D . WPA2 TKIP and 802.1X authentication

Answer: A