Nmap/ZenMap Switches Practice Test

Disabling the port scan while still finding which hosts are alive relies on telling Nmap to perform only host discovery. The flag -sn does exactly this: it runs a host discovery phase and prints only the hosts that respond, with no port scanning attempted. Nmap uses probes like ICMP, ARP, or TCP ping to determine if a host is up, and those that reply are shown in the output.

The other options don’t fit this behavior. A list-style option would only enumerate targets without discovering live hosts. A TCP connect scan performs a port scan. An OS-detection option tries to infer the operating system and typically involves probing ports as part of the process. So the option that matches “disable port scanning but still perform host discovery and show only responding hosts” is the one for host discovery only.