Which of the following is MOST important for an IS auditor to assess during a...

A post-implementation review (PIR) of a newly modified IT application focuses on ensuring that the system meets business and security requirements effectively. The sufficiency of implemented controls (A) is the most critical aspect because it ensures that security, operational, and compliance controls are functioning correctly. These controls include access controls, data integrity checks, and audit logs to prevent unauthorized access, data corruption, or security breaches.

Other options:

Resource management plan (B) is important for project management but is not the primary concern for an IS auditor in a post-implementation review.

Updates required for end-user manuals (C) are necessary for usability but do not impact the security or operational integrity of the system.

Rollback plans for changes (D) are important for change management but are typically assessed before deployment, not in a PIR.