According to the CCAK Study Guide, the business continuity management and operational resilience strategy of the cloud customer should be formulated jointly with the cloud service provider, as they share the responsibility for ensuring the availability and recoverability of the cloud services. The strategy should cover all aspects of business continuity and resilience planning, taking inputs from the assessed impact and risks, to consider activities for before, during, and after a disruption. These activities include prevention, mitigation, response, recovery, restoration, and improvement. The strategy should also define the roles and responsibilities of both parties, the communication channels and escalation procedures, the testing and exercising plans, and the review and update mechanisms1 The other options are not correct because:
* Option B is not correct because the strategy should not only be developed within the acceptable limits of the risk appetite, but also aligned with the business objectives and stakeholder expectations of both parties. The risk appetite is only one of the factors that influence the strategy formulation1
* Option C is not correct because the strategy should not only cover the activities required to continue and recover prioritized activities within identified time frames and agreed capacity, but also consider the activities for before and after a disruption, such as prevention, mitigation, improvement, etc. The strategy should also include other elements such as roles and responsibilities, communication channels, testing plans, etc1 References: 1: ISACA, Cloud Security Alliance. Certificate of Cloud Auditing Knowledge (CCAK) Study Guide. 2021. pp. 83-84.

ISO/IEC 15027017 is a cloud-specific security standard that provides guidelines for information security controls applicable to the provision and use of cloud services. It is based on ISO/IEC 27002, which is a general standard for information security management, but it also includes additional controls and implementation guidance that specifically relate to cloud services. ISO/IEC 15027017 is intended to help both cloud service providers and cloud service customers to enhance the security and confidentiality of their cloud environment and to comply with relevant regulatory requirements and industry standards.12 References := ISO/IEC
27017:2015 - Information technology - Security techniques - Code of practice for information security controls based on ISO/IEC 27002 for cloud services1; Cloud Security Standards: ISO, PCI, GDPR and Your Cloud - Exabeam3; ISO/IEC 27017 - Wikipedia2

The optimal and most efficient mechanism to assess the controls that the provider is responsible for is to review third-party audit reports. Third-party audit reports are independent and objective assessments of the provider's security, compliance, and performance, conducted by qualified and reputable auditors. Third-party audit reports can provide assurance and evidence that the provider meets the industry standards and best practices, as well as the contractual and legal obligations with the SaaS company. Third-party audit reports can also cover a wide range of controls, such as data security, encryption, identity and access management, incident response, disaster recovery, and service level agreements. Some examples of third-party audit reports are ISO 27001 certification, SOC 1/2/3 reports, CSA STAR certification, and FedRAMP authorization123.
Reviewing the provider's published questionnaires (A) may not be optimal or efficient, as the published questionnaires may not be comprehensive or up-to-date, and may not reflect the actual state of the provider's controls. The published questionnaires may also be biased or inaccurate, as they are produced by the provider themselves.
Directly auditing the provider may not be feasible or necessary, as the independent contractor may not have access to the provider's environment or data, and may not have the authority or expertise to conduct such an audit. The independent contractor should rely on the third-party audit reports and certifications to assess the provider's compliance with relevant standards and regulations.
Sending a supplier questionnaire to the provider (D) may not be optimal or efficient, as the supplier questionnaire may not cover all the aspects of the provider's controls, and may not provide sufficient evidence or assurance of the provider's security maturity. The supplier questionnaire may also take a long time to complete and verify, and may not be consistent with the industry standards and best practices. References :=
* How to Evaluate Cloud Service Provider Security (Checklist)
* Cloud service review process - Cloud Adoption Framework
* How to choose a cloud service provider | Microsoft Azure

Mapping the Cloud Controls Matrix (CCM) to other international standards and regulations allows cloud service providers (CSPs) and customers to align their security and compliance measures with a broad range of industry-accepted frameworks. This alignment helps in simplifying compliance processes by ensuring that fulfilling the controls in the CCM also satisfies the requirements of the mapped standards and regulations. It reduces the need for multiple assessments and streamlines the compliance and security efforts, making it more efficient for both CSPs and customers to demonstrate adherence to various regulatory requirements.
References = The benefits of CCM mapping are discussed in resources provided by the Cloud Security Alliance (CSA), which detail how the CCM's controls are aligned with other security standards, regulations, and control frameworks, thus aiding organizations in their compliance and security strategies12.

The greatest risk associated with hidden interdependencies between cloud services is the lack of visibility over the cloud service providers' supply chain. Hidden interdependencies are the complex and often unknown relationships and dependencies between different cloud services, providers, sub-providers, and customers.
These interdependencies can create challenges and risks for the security, availability, performance, and compliance of the cloud services and data. For example, a failure or breach in one cloud service can affect other cloud services that depend on it, or a change in one cloud provider's policy or contract can impact other cloud providers or customers that rely on it.12 The lack of visibility over the cloud service providers' supply chain means that the customers do not have enough information or control over how their cloud services and data are delivered, managed, and protected by the providers and their sub-providers. This can expose the customers to various threats and vulnerabilities, such as data breaches, data loss, service outages, compliance violations, legal disputes, or contractual conflicts.
The customers may also face difficulties in monitoring, auditing, or verifying the security and compliance status of their cloud services and data across the supply chain. Therefore, it is important for the customers to understand the hidden interdependencies between cloud services and to establish clear and transparent agreements with their cloud providers and sub-providers regarding their roles, responsibilities, expectations, and obligations.3 References := How to identify and map service dependencies - Gremlin1; Mitigate Risk for Data Center Network Migration - Cisco2; Practical Guide to Cloud Service Agreements Version 2.03; HIDDEN INTERDEPENDENCIES BETWEEN INFORMATION AND ORGANIZATIONAL ...