What is a requirement to enable Cisco IOS IPS with 5.x signature?

A.
Disable Zone-Based Firewall as the two features are not compatible

B.
Disable Cisco Express Forwarding as the two features are not compatible

C.
Generate a certificate and export on Cisco.com to receive a signature update

D.
Import the public RSA key from the Cisco IPS team that allows the router to verify that a
signature update (which was signed by this key) comes from Cisco