Business processes should be the primary focus of an IS auditor when developing a risk-based IS audit program, because they represent the core activities and functions of the organization that support its objectives and goals. Business processes also involve the use of IT resources and systems that may pose risks to the organization's performance and compliance. A risk-based IS audit program should identify and assess the risks associated with the business processes and determine the appropriate audit scope and procedures to provide assurance on their effectiveness and efficiency. Portfolio management, business plans, and IT strategic plans are also relevant factors for developing a risk-based IS audit program, but they are not as important as business processes. References: CISA Review Manual (Digital Version), Chapter 2, Section 2.2.1

The primary reason to perform a risk assessment is to determine the current risk profile of the organization, which is the level of risk exposure and the likelihood and impact of potential threats. This will help the organization to identify and prioritize the risks that need to be addressed and to align the risk management strategy with the business objectives. A risk assessment may also help to achieve compliance, support the BIA, and allocate budget, but these are not the primary reasons. References: ISACA Glossary of Terms, section "risk assessment"

The best answer is C. Local laws and regulations.
ISACA privacy guidance consistently frames data protection policy around compliance with privacy laws, rules, and regulations. ISACA specifically notes that privacy strategies and policies should be reviewed and updated regularly to reflect regulatory changes and ensure compliance. Since data protection obligations are often legally mandated and penalties can be significant, legal and regulatory requirements are the most important consideration when determining review frequency.
Option A. Industry best practices can inform good policy design, but they do not override legal requirements.
Option B. Business objectives matter for alignment, but they are not the strongest driver of review frequency in a privacy context.
Option D. Known international standards can be useful references, but local legal obligations are more binding and more important for determining how often the policy must be revisited.
Therefore, C is the correct answer because compliance with local laws and regulations is the most important driver of how frequently a data protection policy should be reviewed.
References (Official ISACA):
* ISACA Journal, What Is Your Privacy and Data Protection Strategy?.
* ISACA, The Evolving World of Data Privacy: Trends and Strategies.
* ISACA Journal, Privacy Risk Management.
* ISACA Journal, Analyzing Privacy Policies as Data.