Explanation
The best way for an IS auditor to understand the software benefits to the organization would be to review the business case, which is a document that provides the justification and rationale for acquiring a software solution based on its expected costs, benefits, risks, and alignment with the organization's goals and strategies.
The business case helps to evaluate the feasibility and viability of the software acquisition and to support the decision-making process. A feasibility study is a document that analyzes the technical, operational, economic, legal, and social aspects of a software solution to determine its feasibility and suitability for the organization's needs, but it does not necessarily provide a clear indication of the software benefits to the organization. A request for proposal (RFP) is a document that solicits proposals from potential vendors or suppliers for a software solution based on the organization's requirements and specifications, but it does not necessarily provide a clear indication of the software benefits to the organization. The alignment with IT strategy is a factor that influences the software acquisition process and ensures that the software solution supports and enables the organization's IT strategy, but it is not a document that can be reviewed by an IS auditor to understand the software benefits to the organization. References: CISA Review Manual (Digital Version), Chapter 3: Information Systems Acquisition, Development & Implementation, Section 3.1: Business Case Development