The greatest risk to an organization's ability to manage QC processes is the lack of policies and procedures that define the QC objectives, standards, methods, roles, and responsibilities. Without policies and procedures, the QC processes may be inconsistent, ineffective, inefficient, or noncompliant with the relevant regulations and best practices. Policies and procedures provide the foundation and guidance for the QC processes and help to ensure their quality, reliability, and accountability.
References
ISACA CISA Review Manual, 27th Edition, page 253
Quality Control - an overview | ScienceDirect Topics
Quality Control: Meaning, Importance, Definition and Objectives

Coding standards provide field naming conventions, which are rules for naming variables, constants, functions, classes, and other elements in a program. Coding standards help to ensure consistency, readability, maintainability, and portability of code. Program documentation, access control tables, and data flow diagrams are not part of coding standards. References: CISA Review Manual (Digital Version), Chapter 4, Section 4.3.1

Using a continuous auditing module is an audit procedure that would provide the best assurance that an application program is functioning as designed. A continuous auditing module is a software tool that performs automated and continuous testing and monitoring of an application program's inputs, outputs, processes, and controls. A continuous auditing module can help to verify the accuracy, completeness, validity, reliability, and timeliness of the application program's data and transactions. A continuous auditing module can also help to identify and report any errors, anomalies, deviations, or exceptions in the application program's performance or compliance.
The other options are not as effective or relevant as using a continuous auditing module for providing assurance that an application program is functioning as designed. Interviewing business management is a technique for obtaining information and opinions from the users or owners of the application program, but it does not directly test or verify the functionality or quality of the application program. Confirming accounts is a technique for verifying the existence and accuracy of account balances or transactions, but it does not necessarily reflect the design or operation of the application program. Reviewing program documentation is a technique for examining the specifications, requirements, and procedures of the application program, but it does not provide evidence of the actual implementation or execution of the application program.
References:
* ISACA, CISA Review Manual, 27th Edition, 2019, p. 2361
* Continuous audit and monitoring - PwC2

The business case for an information system investment is a document that provides the rationale and justification for the investment, based on the expected costs, benefits, risks, and impacts of the project12. The business case should be available for review until the benefits have been fully realized, because it serves as a baseline for measuring the actual performance and outcomes of the project against the planned ones34. This helps to evaluate the success and value of the investment, and to identify any gaps or issues that need to be addressed5.
References
1: The Business Case for Security - CISA
2: Beyond the Business Case: New Approaches to IT Investment
3: #HowTo: Build a Business Case for Cybersecurity Investment
4: ISACA CISA Certified Information Systems Auditor Exam ... - PUPUWEB
5: The Business Case for Security | CISA