A full interruption test is the most realistic and reliable way to ensure that recovery time objectives (RTOs) are met for an organization's disaster recovery plan (DRP). RTOs are the maximum amount of time that a business can tolerate being offline after a disaster. A full interruption test involves shutting down the primary site and switching over to the backup site, simulating a real disaster scenario. This test can measure the actual time it takes to restore the systems, applications, and functions that are critical for the business continuity. A full interruption test can also reveal any issues or gaps in the DRP that might affect the recovery process.
The other options are not as effective as a full interruption test for ensuring RTOs are met. A cyber resilience test is a type of DR test that focuses on the ability to withstand and recover from cyberattacks. It does not necessarily cover other types of disasters or test the entire DRP. A tabletop test is a low-impact DR test that involves a walkthrough of the DRP with the key stakeholders and staff. It does not involve any actual switching over or testing of the backup systems. A parallel test is a type of DR test that involves running the backup systems alongside the primary systems, without disrupting the normal operations. It does not measure the time it takes to switch over or resume operations at the backup site.
References:
Best Practices For Disaster Recovery Testing
Disaster recovery testing
Disaster Recovery Testing: Everything to Know

Issuing authentication tokens is the most reliable method of preventing unauthorized logon, as it provides a strong form of authentication that requires users to present something they have (the token) and something they know (the personal identification number or PIN) to access the system. Authentication tokens are physical devices that generate a one-time password or code that changes periodically and is synchronized with the authentication server. This makes it difficult for attackers to steal or guess the credentials of legitimate users. Reinforcing current security policies, limiting after-hours usage and installing an automatic password generator are not as reliable as issuing authentication tokens, as they do not provide a strong form of authentication and may still be vulnerable to unauthorized logon attempts. References:
* : [Authentication Token Definition]
* : Authentication | ISACA

Secure code reviews as part of a continuous deployment program are preventive controls. Preventive controls are controls that aim to prevent or avoid undesirable events or outcomes from occurring, such as errors, defects, or incidents. Secure code reviews are activities that examine and evaluate the source code of a software or application to identify and eliminate any vulnerabilities, flaws, or weaknesses that may compromise its security, functionality, or performance. Secure code reviews as part of a continuous deployment program can help prevent or avoid security issues or incidents from occurring by ensuring that the code is secure and compliant before it is deployed to production. The other options are not correct types of controls for secure code reviews as part of a continuous deployment program, as they have different meanings and functions. Detective controls are controls that aim to detect or discover undesirable events or outcomes that have occurred, such as errors, defects, or incidents. Logical controls are controls that use software or hardware mechanisms to regulate or restrict access to IT resources, such as data, systems, or networks.
Corrective controls are controls that aim to correct or rectify undesirable events or outcomes that have occurred, such as errors, defects, or incidents. References: CISA Review Manual (Digital Version), Chapter 3, Section 3.2

The use of open-source software components in IoT devices presents the greatest security risk due to potential vulnerabilities that may exist within the software. These vulnerabilities can be exploited if patches are not applied promptly, and the organization might not have direct control over the software's maintenance and security updates. This risk is amplified in critical manufacturing environments where compromised IoT devices can lead to operational disruptions.
* Physical Security (Option A):While important, theft of IoT devices generally poses less risk compared to a system-wide compromise due to software vulnerabilities.
* Firmware Storage Constraints (Option C):While a limitation, this is a secondary concern compared to exploitable software.
* Devices Not Using Wireless Connectivity (Option D):Wired devices are generally more secure, reducing this as a significant concern.
Reference:ISACA CISA Review Manual, Job Practice Area 4: Protection of Information Assets.