How should UC create the identities of its e-commerce users with the customer community?

Universal Containers (UC)has an existing e-commerce platform and is implementing a new customer community. They do not want to force customers to register on both applications due to concern over the customers experience. It is expected that 25% of the e-commerce customers will utilize the customer community . The e-commerce platform is capable of generating SAML responses and has an existing REST-ful API capable of managing users .

How should UC create the identities of its e-commerce users with the customer community?
A . Use SAMLJIT in the Customer Community to create users when a user tries to login to the community from the e-commerce site.
B. Use the e-commerce REST API to create users when a user self-register on the customer community and use SAML to allow SSO.
C. Use a nightly batch ETL job to sync users between the Customer Community and the e-commerce platform and use SAML to allow SSO.
D. Use the standard Salesforce API to create users in the Community When a User is Created in the e-Commerce platform and use SAML to allowSSO.

Answer: A