Which approach should the Community Cloud consultant recommended to accomplish this?

Universal Containers (UC) just went live with a new Customer Community. UC wants to automatically create Community users for related contacts when a new business opportunity is marked as closed won.

Which approach should the Community Cloud consultant recommended to accomplish this? Select one or more of the following:
A . Use a trigger to create Community users for all related contacts on the account
B . Use a workflow rule to create a task for the administrator with a list of contacts that should be users
C . Send an email to the administrator when the opportunity is marked closed won so they can create users
D . Use a schedule report that alerts the Salesforce administrator of the new contacts

Answer: A