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Which of the following consists of a publicly available set of databases containing domain name registration contact information?

Whois

Whois provides all sorts of information on registrants-technical POCs, who registered the domain, contact numbers, and so on.

Incorrect:

CAPTCHA is a means to distinguish human from machine input, where a text entry or a picture identification requieres a real human to click or enter it.

IANA regulates IP allocation

IETF is a standards organization.