18.$18.$ In WPA2−$2-$Enterprise, which method is used for authentication?

A.$.$ IEEE 802.1$802\mathrm{.}1$X

B.$.$ Pre−$-$shared key ($($PSK)$)$

C.$.$ Counter Mode−$-$CBC MAC Protocol ($($CCMP)$)$

D.$.$ Temporal Key Integrity Protocol ($($TKIP)$)$

19.$19.$ What is the role of the 4−$4-$way handshake in IEEE 802.11$802\mathrm{.}11$i operation?

A.$.$ To authenticate between the wireless device and the access point without transmitting the password

B.$.$ To transfer data between the wireless device and the access point

C.$.$ To enable the wireless device to discover the access point

D.$.$ To negotiate encryption algorithm to be used