Network topology diagrams are the most important for an IS auditor to review when evaluating the design of controls related to network monitoring, because they show how the network components are connected and configured, and what security measures are in place to protect the network from unauthorized access or attacks. Incident monitoring logs, the ISP service level agreement, and reports of network traffic analysis are useful for evaluating the effectiveness and performance of network monitoring, but not the design of controls. References: CISA Review Manual (Digital Version), Chapter 5, Section 5.3.3

A virtual tape library (VTL) is a disk-based backup system that emulates a tape library. It provides faster backup and recovery than traditional tape systems, and it can be integrated with data deduplication and replication technologies to enhance disaster recovery. A VTL can also be replicated to an offsite location for additional protection. A VTL is the best disaster recovery solution for an environment where data virtualization is used, because it can handle large volumes of data, support multiple backup applications, and provide consistent performance.
Onsite disk-based backup systems (A) are not the best disaster recovery solution, because they are vulnerable to the same risks as the primary data center, such as fire, flood, power outage, or sabotage. Tape-based backup systems (B) are not the best disaster recovery solution, because they are slow, prone to errors, and require manual intervention. Redundant array of independent disks (RAID) (D) is not a backup system, but a storage technology that improves performance and fault tolerance by distributing data across multiple disks. RAID does not protect against data corruption, human error, or malicious attacks.
References:
Virtualization Disaster Recovery Overview: Definitions and Guides
Disaster Recovery Virtualization - VMware
What is Virtual Disaster Recovery? - Definition from Techopedia
How Does Virtualization Help With A Disaster Recovery Plan

The best method to prevent wire transfer fraud by bank employees is system-enforced dual control. System- enforced dual control is a segregation of duties control that requires two or more individuals to perform or authorize a transaction or activity using a system that enforces this requirement. System-enforced dual control can prevent wire transfer fraud by requiring independent verification and approval of payment requests, amounts, and recipients by different bank employees using a system that does not allow any single employee to complete the transaction alone. The other options are not as effective as system-enforced dual control in preventing wire transfer fraud, as they do not involve independent checks or approvals using a system.
Independent reconciliation is a detective control that can help compare and confirm payment records with bank statements, but it does not prevent wire transfer fraud from occurring. Re-keying of wire dollar amounts is an input control that can help detect any errors or discrepancies in payment amounts, but it does not prevent wire transfer fraud from occurring. Two-factor authentication control is an access control that can help verify the identity and authorization of bank employees, but it does not prevent wire transfer fraud from occurring. References: CISA Review Manual (DigitalVersion), Chapter 3, Section 3.2