When implementing a 1:1 relationship, where should you place the foreign key if one side is mandatory and one side is optional? Should the foreign key be mandatory or optional?

Austin rare coins, inc., buys and sells rare coins, bullion, and other precious metals through eight web sites with different domain names. an unknown individual took control of austin's servers and transferred the domain names to another registrant without austin's permission. the new registrant began using the domain names to host malicious content—including hate letters to customers and fraudulent contact information—and to post customers' credit-card numbers and other private information, thereby tarnishing austin's goodwill. austin filed a suit in a federal district court against the new registrant under the anticybersquatting consumer protection act. is austin entitled to a transfer of the domain names? austin rare coins, inc., buys and sells rare coins, bullion, and other precious metals through eight web sites with different domain names