The most effective method to verify that a service vendor keeps control levels as required by the client is to conduct periodic on-site assessments using agreed-upon criteria. On-site assessments can provide direct evidence of whether the vendor's controls are operating effectively and consistently in accordance with the client's expectations and requirements. Agreed-upon criteria can ensure that the assessments are objective, relevant, and reliable. The other options are not as effective as on-site assessments in verifying the vendor's control levels. Periodically reviewing the SLA with the vendor can help monitor whether the vendor meets its contractual obligations and service standards, but it does not provide assurance of whether the vendor's controls are adequate or sufficient. Conducting an unannounced vulnerability assessment of vendor's IT systems can help identify any weaknesses or gaps in the vendor's security controls, but it may violate the terms and conditions of the vendor-client relationship or cause operational disruptions. Obtaining evidence of the vendor's CSA can provide some indication of whether the vendor's controls are self-monitored and reported, but it does not verify whether the vendor's controls are independent or accurate. References: CISA Review Manual (Digital Version), Chapter 5, Section 5.4

The effectiveness of an organization's security awareness program can be measured by capturing data on changes in the way people react to threats, such as the ability to recognize and avoid social engineering attacks1. An increase in the number of phishing emails reported by employees indicates that they are more aware of the signs and risks of phishing, and are more likely to take appropriate actions to prevent or mitigate the impact of such attacks23.
References
1: The Importance Of Measuring Security Awareness 2: Measuring the effectiveness of your security awareness program 3: How effective is security awareness training?

The most important thing to include in forensic data collection and preservation procedures is preserving data integrity. Data integrity is the property that ensures that data is accurate, complete, and consistent throughout its lifecycle. Preserving data integrity is essential for forensic data collection and preservation procedures because it ensures that the data can be used as valid and reliable evidence in legal proceedings or investigations. Preserving data integrity can be achieved by using methods such as hashing, checksums, digital signatures, write blockers, tamper-evident seals, or timestamps. The other options are not as important as preserving data integrity in forensic data collection and preservation procedures, as they do not affect the validity or reliability of the data. Assuring the physical security of devices is a security measure that protects devices from unauthorized access, theft, damage, or destruction, but it does not ensure that the data on the devices is accurate, complete, and consistent. Maintaining chain of custody is a documentation technique that records and tracks the handling and transfer of devices or data among different parties involved in forensic activities, but it does not ensure that the data on the devices is accurate, complete, and consistent. Determining tools to be used is a planning activity that selects and prepares the appropriate tools for forensic data collection and preservation procedures, but it does not ensure that the data collected and preserved by the tools is accurate, complete, and consistent. References: CISA Review Manual (Digital Version), Chapter 5, Section 5.4