Which of the following choices must be installed on a MID Server to run Credential-less...

Credential-less Discovery is a feature of ServiceNow Discovery that allows the instance to identify configuration items (CIs) without using credentials. Credential-less Discovery uses Network Mapper (Nmap), a free and open-source network scanner, to collect information about the CIs by sending packets and analyzing the responses. Nmap must be installed on the MID Server that runs Credential-less Discovery. Credential-less Discovery can be used as a fallback option when credential-based probes fail, or as a primary option for scanning certain types of devices, such as network devices, printers, or IoT devices12.

References:

Credential-less Discovery with Nmap - Product Documentation: San Diego - Now Support Portal

Credential-less host Discovery - ServiceNow - Now Support