The correct answer is: B. .com
A top-level domain (TLD) is the last part of a domain name, such as .com, .net, or .org. TLDs are used to identify the type of organization or website. For example, .com is used for commercial websites, .net is used for network-related organizations, and .org is used for non-profit organizations.
The .com TLD is the most popular TLD in the world, accounting for over 40% of all websites. It was created in 1985 and is intended for general use. Any organization or individual can register a .com domain name.
The other options are not open extensions available for general use. .xyz is a new TLD that was created in 2014. It is intended for general use, but it is not as popular as .com. .cn is a country-code TLD for China. .edu is a country-code TLD for educational institutions in the United States.