Preventive controls are the most suitable for a system identified as critical in terms of data and function to the organization, because they aim to prevent or deter threats from compromising the system's confidentiality, integrity, and availability. Examples of preventive controls include encryption, authentication, access control, firewalls, antivirus software, and backup systems. Monitoring, cost, and compensating controls are not as effective as preventive controls for protecting critical systems, because they either detect, measure, or mitigate the impact of threats after they have occurred, rather than preventing them in the first place. References:
CISSP All-in-One Exam Guide, Eighth Edition, Chapter 1: Security and Risk Management, page 22. Official (ISC)2 CISSP CBK Reference, Fifth Edition, Chapter 1: Security and Risk Management, page 35.

The level of logging will be according to your company requirements. Below is a list of items that could be logged, please note that some of the items may not be applicable to all operating systems. What is being logged depends on whether you are looking for performance problems or security problems. However you have to be careful about performance problems that could affect your security.

CCTV cameras fall under the category of physical surveillance.
Answers a and b are forms of active surveillance. These types of surveillance require an organizational policy informing the employees that the surveillance is being conducted. Additionally, warning banners describing the surveillance at log-on to a computer or network should
be prominently displayed. These banners usually state that by logging
on, the user acknowledges the warning and agrees to the monitoring.
Answer "Review of audit logs" is a passive form of computer/network surveillance.

Level A1 is described as Verified Design.
The following answers are incorrect:
B3. This is incorrect because level B3 is described as Security Domains.
B2. This is incorrect because level B2 is described as Structured Protection.
B1. This is incorrect because level B1 is described as Labeled Security.