Which of these is an administrative time saving benefit of dynamic signature definition files on a Cisco router running Cisco IOS IPS?

A.
Dynamically learns new signatures in real time

B.
Dynamically updates signatures from cisco.com

C.
Dynamically configures IPS signature parameters

D.
Dynamically chooses which signatures to activate based upon network traffic seen

Explanation:
http://www.cisco.com/en/US/docs/ios/12_3t/12_3t8/feature/guide/gt_fwids.html
A Signature Definition file (SDF) has definitions for each signature it contains. After signatures are loaded and complied onto a router running Cisco IOS IPS, IPS can begin detecting the new signatures immediately. If customers do not use the default, built-in signatures that are shipped with the routers, users can choose to download one of two different types of SDFs: the attack-drop.sdf file (which is a static file) or a dynamic SDF (which is dynamically updated and accessed from Cisco.com).