How does PEAP protect the EAP exchange?

How does PEAP protect the EAP exchange?

A.
It encrypts the exchange using the server certificate.

B.
It encrypts the exchange using the client certificate.

C.
It validates the server-supplied certificate, and then encrypts the exchange using the client certificate.

D.
It validates the client-supplied certificate, and then encrypts the exchange using the server certificate.