The best way to prevent the misconfiguration from recurring is to grant user access using a role-based model. A role-based access control (RBAC) model is an access control method that assigns permissions to end-users based on their role within the organization1. RBAC provides fine-grained control, offering a simple, manageable approach to access management that is less error-prone than individually assigning permissions1. RBAC also enforces the principle of least privilege, which means that users only have the minimum access required to perform their tasks2.
A role-based model can help prevent segregation of duties (SoD) issues in an ERP system by restricting user access to conflicting activities within the application. SoD is a central issue for enterprises to ensure compliance with laws and regulations, and to reduce the risk of fraud and unauthorized transactions3. SoD requires that no single individual or group of individuals should have control over two or more parts of a process or an asset3. For example, a user who can create and approve purchase orders should not be able to process payments or modify vendor records.
By using a role-based model, user access provisioning is based on the needs of a group (e.g., accounting department) based on common responsibilities and needs1. This means each role has a given set of permissions, and individuals can be assigned to one or more roles. For example, you may designate a user as an accounts payable clerk, an accounts receivable clerk, or a financial manager, and limit access to specific resources or tasks. The user-role and role-permissions relationships make it easy to perform role assignment because individual users no longer have unique access rights, rather they have privileges that conform to the permissions assigned to their specific role or job function1.
The other options are not the best way to prevent the misconfiguration from recurring. Monitoring access rights on a regular basis (option A) is a detective control that can help identify SoD issues after they occur, but it does not prevent them from happening in the first place. Referencing a standard user-access matrix (option B) is a tool that can help document and analyze user access rights, but it does not ensure that the user access rights are configured correctly or consistently. Correcting the segregation of duties conflicts (option D) is a corrective action that can resolve SoD issues once they are detected, but it does not prevent them from happening again.
References: 3: Implementing Segregation of Duties: A Practical Experience Based on Best Practices 1: What is Role-Based Access Control (RBAC)? Examples, Benefits, and More 2: What is Azure role-based access control (Azure RBAC)?

The programmer having access to the production programs is a control weakness that would have contributed most to the problem of unauthorized changes to key fields in a payroll system report. This is because it violates the principle of segregation of duties, which requires that different individuals or groups perform different functions related to system development, testing, implementation, and operation. Allowing programmers to access production programs increases the risk of errors, fraud, or malicious actions that may compromise the integrity, availability, or confidentiality of the system or its data. The other options are not as significant as having access to production programs, as they relate to other aspects of system development or maintenance, such as user involvement in testing (which affects user satisfaction and acceptance), user requirements documentation (which affects system functionality and quality), and payroll files control (which affects data security and accuracy). References: CISA Review Manual (Digital Version), Domain 3:
Information Systems Acquisition, Development and Implementation, Section 3.2 Project Management Practices

The best assurance of data integrity after file transfers is hash values. Hash values are unique strings that are generated by applying a mathematical function to the data. Hash values can be used to verify that the data has not been altered or corrupted during the transfer, as any change in the data would result in a different hash value. By comparing the hash values of the source and destination files, one can confirm that the data is identical and intact.
The other options are not as effective as hash values for ensuring data integrity after file transfers. Check digits are digits added to a number to detect errors in data entry or transmission, but they are not reliable for detecting intentional or complex modifications of the data. Monetary unit sampling is a statistical sampling technique used for auditing financial statements, but it is not applicable for verifying data integrity after file transfers. Reasonableness check is a validation method that checks whether the data falls within an expected range or format, but it does not guarantee that the data is accurate or consistent with the source.
References:
* 5: On Windows, how to check that data is unchanged after copying? - Super User
* 6: Data integrity | Cloud Storage Transfer Service Documentation | Google Cloud
* 7: Checking File Integrity - HECC Knowledge Base
* 8: How to setup File Transfer Integrity Checks - Progress.com

The proximity badge incorrectly granting access to restricted areas is the most concerning issue, as it indicates a failure of the access control system to enforce the principle of least privilege and protect the sensitive or critical assets of the organization. The proximity badge should only grant access to the areas that are necessary for the IS auditor to perform the audit fieldwork, and not to any other areas that may contain confidential information, valuable equipment, or hazardous materials. The incorrect access could result in unauthorized disclosure, modification, or destruction of the assets, as well as potential safety or legal issues.
References
ISACA CISA Review Manual, 27th Edition, page 254
Office & Workplace Physical Security Assessment Checklist
Physical Security: Planning, Measures & Examples