What would be considered the biggest drawback of Host-based Intrusion Detection systems (HIDS)?

A.
It can be very invasive to the host operating system

B.
Monitors all processes and activities on the host system only

C.
Virtually eliminates limits associated with encryption

D.
They have an increased level of visibility and control compared to NIDS

Explanation:
Because the HIDS uses the resources of the host, it can be very invasive.
Incorrect Answers:
B, C, D: Advantages of HIDS includes:
Monitoring of host local events (reveals attacks not detectable by NIDS).
Works well even if traffic is encrypted.
When it works on OS audit trails it can reveal Trojan Horse or other attacks to SW integrity.

http://www.federica.unina.it/ingegneria/security-and-dependability-of-computer-systems/intrusion-detectionsystemarchitectures/