Which is a valid way of injecting a container-managed transaction-scoped persistence context into an EJB 3.0 session…?

Which is a valid way of injecting a container-managed transaction-scoped persistence context into
an EJB 3.0 session bean assuming the application contains only one persistence unit?

A.
@PersistenceUnit public EntityManager em;

B.
@PersistenceContext private EntityManager em;

C.
@TransactionManagement(TransactionManagementType. CONTAINER) public EntityManager
em;

D.
@Resource(name=”persistence/em”, authenticationType=AuthenticationType. CONTAINER)

protected EntityManager em;