Which statement is true about an External ID field? (Choose two.)

Cloud Kicks (CK) is finding sales reps are inconsistent in data entry when deals are won. CK requires that custom shoes are shipped within two weeks after the close date. A custom field called Scheduled Ship Date on the opportunity records the ship date.
How should the app builder ensure this field is properly filled out before setting the opportunity to closed won?

Which two objects can be members of a Campaign? (Choose two.)

What is a use case for approval processes? Choose 2 answers.

If a field update for Rule1 triggers Rule2, and a field update for Rule2 triggers Rule1 ___________.