How many layers are incorporated in IPS detection and what are they called?

How many layers are incorporated in IPS detection and what are they called?
A . 4 layers C Passive Streaming Library (PSL), Protocol Parsers, Context Management, Protections
B . 3 layers C Active Streaming Library (ASL), CMI, Protections
C . 4 layers C Active Streaming Library (ASL), Protocol Parsers, Context Management, Protections
D . 3 layers C Protocol Parsers, CMI, Protections

Answer: A