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

A router is a type of device that sits on the perimeter of a corporate or home network, where it obtains a public IP address and then generates private IP addresses internally. A router connects two or more networks and forwards packets between them based on routing rules. A router can also provide network address translation (NAT) functionality, which allows multiple devices to share a single public IP address and access the internet. A switch is a type of device that connects multiple devices within a network and forwards packets based on MAC addresses. An intrusion prevention system (IPS) is a type of device that monitors network traffic and blocks or modifies malicious packets based on predefined rules. A gateway is a type of device that acts as an interface between different networks or protocols, such as a modem or a firewall. References: CISA Review Manual (Digital Version), [ISACA Glossary of Terms]

Implementing business rules to validate employee data entry is the best way to reduce the likelihood of future occurrences of poor data quality that cause customer complaints about receiving different items from what they ordered on the organization's website. Business rules are logical statements that define the conditions and actions for data validation, such as checking for data completeness, accuracy, consistency, and integrity. Assigning responsibility for improving data quality, investing in additional employee training for data entry, and outsourcing data cleansing activities to reliable third parties are also possible ways to improve data quality, but they are not as effective as implementing business rules to validate employee data entry. References: CISA Review Manual (Digital Version), Chapter 4, Section 4.3.1

Parallel processing is a system implementation approach that involves running the new system and the old system simultaneously for a period of time until the new system is verified and accepted. The primary advantage of parallel processing is that it provides assurance that the new system meets performance requirements and produces the same or better results as the old system. Parallel processing also minimizes the risk of system failure and data loss, as the old system can be used as a backup or fallback option in case of any problems with the new system.

IT disaster recovery time objectives (RTOs) are the maximum acceptable time that an IT system can be unavailable after a disaster before it causes unacceptable consequences for the business. IT RTOs should be based on the business-defined criticality of the systems, which reflects how important they are for supporting the business processes and functions. The maximum tolerable loss of data, the nature of the outage, and the maximum tolerable downtime (MTD) are also factors that affect the IT RTOs, but they are not the primary basis for determining them.