What should an identity architect recommend to enable single sign-on (SSO) between the portal and Salesforce?

Northern Trail Outfitters (NTO) utilizes a third-party cloud solution for an employee portal. NTO also owns Salesforce Service Cloud and would like employees to be able to login to Salesforce with their third-party portal credentials for a seamless expenence. The third-party employee portal only supports OAuth.

What should an identity architect recommend to enable single sign-on (SSO) between the portal and Salesforce?
A . Configure SSO to use the third party portal as an identity provider.
B. Create a custom external authentication provider.
C. Add the third-party portal as a connected app.
D. Configure Salesforce for Delegated Authentication.

Answer: A