Which of the following is the practice of a domain name registrant using the five-day "grace period" (the Add Grace Period or AGP) at the beginning of the registration of an ICANN-regulated second…

NMap is a network scanning and port discovery tool used for host discovery and security auditing, completely unrelated to domain registration practices.

Domain tasting takes advantage of ICANN's five-day Add Grace Period, originally intended to allow correction of registration errors, by registering domains speculatively to measure click-through ad revenue, then deleting unprofitable domains for a full refund - effectively allowing free temporary use of domain names at scale.

A proxy server is an intermediary server that forwards client requests to other servers for purposes such as anonymity, caching, or access control, and has no relation to domain registration.

PsPasswd is a Sysinternals command-line utility used to change account passwords on local or remote Windows systems, unrelated to domain name registration.