How does the Diameter protocol provide more security than RADIUS?

How does the Diameter protocol provide more security than RADIUS?

A.
For interoperability issues, the both provide the same level of security.

B.
Diameter has been developed to work directly with TLS and IPSec.

C.
Diameter works within the S/MIME standard.

D.
RADIUS only encrypts the username.

Explanation:
Diameter provides end-to-end security through the use of IPSec or TLS,which is not available in RADIUS.