Which two configurations should an app builder recommend?

Sales managers want to be automatically notified any time there is a change to an opportunity close date and want these changes to be tracked on the opportunity.

Which two configurations should an app builder recommend? Choose 2 answers
A . Create an opportunity outbound message
B . Activate historical trending for opportunities
C . Enable feed tracking on opportunities
D . Use process builder on opportunities and a chatter post action

Answer: C,D