A configuration management system is a process that establishes and maintains the consistency of a product's attributes throughout its life cycle. It helps to identify and control the functional and physical characteristics of a product, and to record and report any changes to those characteristics. A configuration management system also supports the audit of the product to verify its conformance to requirements.
One of the key activities of a configuration management system is to define baselines for software. A baseline is a fixed reference point that serves as a basis for comparison and measurement. A baseline can be established for any configuration item, such as a requirement, a design document, a test plan, or a software component. A baseline helps to ensure that the software product meets its intended purpose and quality standards, and that any changes to the software are controlled and documented.
A configuration management system also supports other activities, such as tracking software updates, supporting the release procedure, and standardizing change approval, but these are not its primary purpose.
Therefore, the other options are incorrect.
References: : What is configuration management - Red Hat : Configuration Management | Definition, Importance and Benefits - ServerWatch

A project business case is a document that describes the rationale and justification for initiating a project, based on its expected costs, benefits, risks, and feasibility. A project business case provides the most useful information to an IS auditor when selecting projects for inclusion in an IT audit plan, because it helps the IS auditor to:
Understand the purpose, scope, objectives, and deliverables of the project Assess the alignment of the project with the organization's strategy, vision, and goals Evaluate the value proposition and return on investment of the project Identify the key stakeholders, sponsors, and owners of the project Analyze the potential risks and issues associated with the project Compare and prioritize the project with other competing projects The other possible options are:
A). Project charter: A project charter is a document that formally authorizes and defines the high-level scope, roles, responsibilities, and authority of a project. A project charter provides some useful information to an IS auditor when selecting projects for inclusion in an IT audit plan, but it is not the most useful information. A project charter does not provide enough details about the costs, benefits, risks, and feasibility of the project, which are essential for evaluating its suitability for an IT audit plan.
B). Project plan: A project plan is a document that outlines the detailed scope, schedule, budget, resources, quality, and communication plans of a project. A project plan provides some useful information to an IS auditor when selecting projects for inclusion in an IT audit plan, but it is not the most useful information. A project plan does not provide enough information about the rationale, justification, value proposition, and alignment of the project with the organization's strategy and goals, which are important for assessing its relevance for an IT audit plan.
C). Project issue log: A project issue log is a document that records and tracks the issues that arise during a project's execution and how they are resolved. A project issue log provides some useful information to an IS auditor when selecting projects for inclusion in an IT audit plan, but it is not the most useful information. A project issue log does not provide enough information about the purpose, objectives, benefits, and feasibility of the project, which are critical for determining its priority for an IT audit plan.

Using analytical tools to produce exception reports from the system and performance monitoring software is the most effective plan of action for a company that purchased and implemented system and performance monitoring software. Exception reports are reports that highlight deviations or anomalies from predefined thresholds or standards. Using analytical tools to produce exception reports can help to reduce the size and complexity of the system and performance monitoring reports, as well as to focus on the most relevant and critical information for review and action. The other options are less effective plans of action, as they may involve unnecessary costs, risks, or efforts. References:
CISA Review Manual (Digital Version), Chapter 4, Section 4.2.21
CISA Review Questions, Answers and Explanations Database, Question ID 219

The most important thing for an IS auditor to determine during the detailed design phase of a system development project is that acceptance test criteria have been developed. Acceptance test criteria define the expected functionality, performance and quality of the system, and are used to verify that the system meets the user requirements and specifications. The IS auditor should ensure that the acceptance test criteria are clear, measurable and agreed upon by all stakeholders. Program coding standards have been followed is something that the IS auditor should check during the coding or testing phase, not the detailed design phase.
Data conversion procedures have been established or the design has been approved by senior management are things that the IS auditor should verify during the implementation phase, not the detailed design phase. References: ISACA, CISA Review Manual, 27th Edition, 2018, page 323