NFS Enumeration is the correct choice because the scenario is centered on TCP port 2049 and the use of a standard utility to list exported remote file systems. In CEH-aligned reconnaissance and enumeration, port 2049 is the primary service port for Network File System NFS. When a tester identifies 2049 as open on a Linux or UNIX-like host, a common next step is to enumerate NFS exports to learn which directories are shared and what access rules apply. The “standard utility” described is consistent with tools such as showmount, which queries the target to retrieve a list of exported file systems and, in some cases, the clients allowed to mount them. This directly supports the stated objective of “requesting a list of remote file systems shared across the network” to map accessible resources.

The distractor checks mentioned in the scenario reinforce why the answer is NFS. Telnet enumeration would relate to TCP 23 and interactive plaintext terminal access, not file-share exports. NTP enumeration aligns to UDP 123 and focuses on time synchronization information and server behavior, not shared directories. SNMP enumeration typically involves UDP 161 and extracts device and system details via community strings and management information bases. NetBIOS enumeration is associated with Windows networking services such as UDP 137 and TCP 139, which are unrelated to NFS on 2049.

Therefore, the active enumeration method demonstrated is NFS enumeration through export listing on TCP port 2049.