Partitioning the work environment from personal space on devices. This would best maintain information security without compromising employee privacy by creating a separate and secure area on the personal mobile devices for work-related data and applications. This way, the organization can protect its information from unauthorized access, loss, or leakage, while respecting the employees' personal data and preferences on their own devices.
The other options are not as effective as option B in balancing information security and employee privacy.
Option A, installing security software on the devices, is a good practice but may not be sufficient to prevent data breaches or comply with regulatory requirements. Option C, preventing users from adding applications, is too restrictive and may interfere with the employees' personal use of their devices. Option D, restricting the use of devices for personal purposes during working hours, is impractical and difficult to enforce.
References:
* ISACA, CISA Review Manual, 27th Edition, 2019
* ISACA, CISA Review Questions, Answers & Explanations Database - 12 Month Subscription
* Personal Cellphone Privacy at Work1
* Protecting your personal information and privacy on a company phone2
* Mobile Devices and Protected Health Information (PHI)3
* Using your personal phone for work? Here's how to separate your apps and data4
* 9 Ways to Improve Mobile Security and Privacy in the Age of Remote Work5

Restricting program functionality according to user security profiles is the best control for ensuring appropriate segregation of duties within an accounts payable department. An IS auditor should verify that the access rights and permissions of the accounts payable staff are based on their roles and responsibilities, and that they are not able to perform incompatible or conflicting functions such as creating, approving, or paying invoices. This will help to prevent fraud, errors, or abuse of authority within the accounts payable process.
The other options are less effective controls for ensuring segregation of duties, as they may involve audit trails, access restrictions, or user identification. References:
* CISA Review Manual (Digital Version), Chapter 6, Section 6.31
* CISA Review Questions, Answers & Explanations Database, Question ID 223

The auditor implemented a specific control during the development of the system. This would impair the auditor's independence, as it would create a self-review threat, which is a situation where an auditor has to evaluate or review the results of his or her own work or judgment1. A self-review threat may compromise the auditor's objectivity and impartiality, as the auditor may be biased or influenced by his or her own involvement or interest in the system1. The auditor may also face a conflict of interest or a loss of credibility if he or she has to report on any issues or deficiencies related to the control he or she implemented.