What recommendation should an architect make to meet this requirement?

Universal containers (UC) uses an internal company portal for their employees to collaborate. UC decides to use salesforce ideas and provide the ability for employees to post ideas from the company portal. They use SAML-BASED SSO to get into the company portal and would like to leverage it to access salesforce. Most of the users don’t exist in salesforce and they would like the user records created in salesforce communities the first time they try to access salesforce .

What recommendation should an architect make to meet this requirement?
A . Use on-the-fly provisioning
B . Use just-in-time provisioning
C . Use salesforce APIs to create users on the fly
D . Use Identity connect to sync users

Answer: B