ISA/IEC 62443-2-1 clearly recommends that the IACS Security Program (SP) be fully embedded into existing organizational processes, including alignment with the Information Security Management System (ISMS), if present.
"The IACS security program shall be integrated with the organization's overall management systems and processes, including those defined in the ISMS (e.g., ISO/IEC 27001)."
- ISA/IEC 62443-2-1:2010, Clause 4.2.1 - Integration of Security Program This ensures that security is a sustained operational priority and not a separate or siloed initiative.
References:
ISA/IEC 62443-2-1:2010 - Clause 4.2.1
ISO/IEC 27001 - ISMS alignment

The three general classes of firewalls are:
Packet Filtering Firewalls - Basic filters based on IPs, ports, protocols Stateful Inspection Firewalls - Track active connections and session state Application Proxy Firewalls - Act as intermediaries at the application layer
"Network inspection" is not a standard firewall classification, but rather a general term that may refer to DPI (Deep Packet Inspection) or NIDS (Network Intrusion Detection Systems).
"Firewall technologies are typically classified into packet filtering, stateful inspection, and application proxy types."
- ISA/IEC 62443-3-3:2013, SR 5.1 - Zone Boundary Protection
References:
ISA/IEC 62443-3-3:2013 - Clause SR 5.1
NIST SP 800-41 - Guidelines on Firewalls and Firewall Policy

ISA/IEC 62443-1-3 is specifically titled "System Security Conformance Metrics" and introduces a methodology to develop quantitative metrics for assessing how well a system conforms to the ISA/IEC 62443 requirements.
"Part 1-3 defines a set of metrics to quantitatively measure the conformance of systems and components to the ISA/IEC 62443 series. It supports repeatable assessment and benchmarking."
- ISA/IEC 62443-1-3:2013, Scope and Clause 5
This allows organizations to establish measurable KPIs and drive continuous improvement in IACS cybersecurity programs.
References:
ISA/IEC 62443-1-3:2013 - Scope and Methodology Section
ISA/IEC 62443-1-1 - Relationship to other parts

In ANSI/ISA-99.00.01:2007, which is part of the ISA/IEC 62443 standards, electronic security encompasses both the technical and human aspects of cybersecurity within industrial automated and control systems (IACS). Option B correctly highlights components such as computers, networks, operating systems, applications, and other programmable configurable components which are intrinsic to the system's electronic security framework. Option C is also correct as it includes the personnel, policies, and procedures which play a crucial role in securing these systems. This emphasizes that security is not only about the technological solutions but also about managing human elements and organizational processes effectively.
ISA/IEC 62443 Cybersecurity Fundamentals References:
ISA/IEC 62443 standards focus on the holistic nature of security which is clearly supported by including both the technological (Option B) and human elements (Option C) in the definition of electronic security.

OPC Classic uses Microsoft's DCOM (Distributed Component Object Model) for communication, which dynamically opens multiple ports, making it extremely difficult to manage with firewalls.
"OPC Classic is firewall-unfriendly because DCOM requires dynamic port negotiation, making it difficult to define consistent firewall rules."
- ISA/IEC 62443-3-3:2013, Annex A - Communication Protocols and Security Concerns This lack of port predictability presents a significant security and operational risk, which led to the development of OPC UA, which uses fixed ports and supports encryption.
References:
ISA/IEC 62443-3-3 - Annex A
OPC Foundation Security Guidelines