The correct answer is B because the Credentials tab in NetworkMiner is specifically used to display usernames, passwords, and other credential material extracted from packet captures. NetworkMiner documentation and walkthroughs describe the tool as capable of parsing PCAP data to extract higher-layer artifacts, including files, emails, certificates, and credentials. Since the investigators want a consolidated view of usernames and passwords before moving on to other analysis tasks, the Credentials tab is the most direct place to look. Files would be used for reconstructed transferred objects, Hosts for endpoint and traffic summaries, and Sessions for conversation-level details, but none of those is the dedicated credential view.
CHFI v11 includes network forensics and packet analysis, so candidates are expected to know not only which tools are useful, but also which specific interfaces within those tools support a given investigative objective.
When the aim is quick triage of possible usernames and passwords observed in network traffic, the proper NetworkMiner tab is Credentials.