How does NBAR differ from traditional TCP/UDP packet recognition?

A.
NBAR queries each application directly

B.
NBAR uses different port numbers than TCP/UDP

C.
NBAR builds a database of packet types

D.
NBAR looks into the payload for application clues

Explanation:
Page 185, IP Telephony Self-Study Cisco DQOS Exam Certification Guide, http//www.ciscopress.com/title/1587200589