Which statement is true about the use of a persist operation in a transaction?

Which statement is true about the use of a persist operation in a transaction?

A.
If a user persists a detached object it always becomes managed.

B.
The persist operation on an entity always cascades to its related entities.

C.
If a user persists a new entity with an existing primary key the transaction will fail.

D.
If a user persists a managed entity an exception may be thrown by the persist operation.