What improvement does EAP-FASTv2 provide over EAP-FAST?

A.
It allows multiple credentials to be passed in a single EAP exchange.

B.
It supports more secure encryption protocols.

C.
It allows faster authentication by using fewer packets.

D.
It addresses security vulnerabilities found in the original protocol.

Explanation:
BD
As an enhancement to EAP-FAST, a differentiation was made to have a User PAC and a Machine PAC. After a
successful machine-authentication, ISE will issue a Machine-PAC to the client. Then, when processing a user-authentication, ISE will request the Machine-PAC to prove that the machine was successfully authenticated,
too. This is the first time in 802.1X history that multiple credentials have been able to be authenticated within
a single EAP transaction, and it is known as “EAP Chaining”.
Source: http://www.networkworld.com/article/2223672/access-control/which-eap-types-do-you-need-for-whichidentity-projects.html