Wireshark is a network protocol analyzer that allows analysts to capture and inspect data packets traveling through a network. This makes it ideal for investigating unusual network activity, as it provides detailed insights into the nature and content of network traffic. In this case, Wireshark can help identify potentially malicious packets and understand the nature of the observed traffic. Options A (WAF) and C (EDR) are primarily used for monitoring and protecting web applications and endpoints, respectively, and Nmap (D) is typically used for network discovery and mapping, not detailed traffic analysis. According to CompTIA CySA+, packet analysis tools like Wireshark are invaluable for deep-dive investigations into network anomalies.