How can the Salesforce Admin limit the membership of this new community to US customers?

Universal Containers has a customer Community in Europe and plans to roll out as

separate Community for their US customers. They have separate profiles for the US, Europe, and Asia customers.

How can the Salesforce Admin limit the membership of this new community to US customers?

Select one or more of the following:
A . Add US users to the community sharing set
B . Add each US customer as a Community member from the contact record
C . Add the US customer public group to the Community as members of the Community
D . Add only US customer profiles as Community members

Answer: D