Universal Containers has a Community for partners and another Community for their customers. They want to give their partners access to their Community for customers as well. How should the Salesforce Admin do this?

a. Include the partner profile as a member of the Community for customers
b. Add the Customer community to the Partner Community user profile.
c. Create Partner users as members in the Customer Community and send login details to the users.
d. Select the Enable Customer Community user option in the Partner contact in Salesforce.