Explanation
The most beneficial stage of the system development life cycle (SDLC) to consider data privacy principles is D: Requirements definition. This is because data privacy principles should be integrated into the design and development of customer-facing IT applications from the very beginning, not as an afterthought or a retrofit1. By considering data privacy principles in the requirements definition stage, the developers can identify the personal data that will be collected, processed, stored, and shared by the application, and ensure that they comply with the relevant laws and regulations, such as the General Data Protection Regulation (GDPR)2. They can also apply the principles of data minimization, purpose limitation, transparency, consent, and security to protect the privacy rights and interests of the customers3.

Obtaining user approval of program changes is very effective for controlling application changes and maintenance.

Explanation
Given the large volume of data transactions, continuous monitoring is the best testing strategy for auditing the inventory control process. Continuous monitoring involves the automated review of operational and financial data to identify anomalies or areas of concern12. This approach allows for real-time identification and resolution of issues, making it particularly effective for large organizations with high transaction volumes12.
References: ISACA's Information Systems Auditor Study Materials1