Which two statements are true about the context of an application?

Which two statements are true about the context of an application? (Choose two.)

A.
It is attached to a session.

B.
It is owned by the user SYS.

C.
A user can change the context of his or her application.

D.
The PL/SQL package associated with the context must exist before the context is created.

E.
The predefined attributes in the USERENV application context can be changed as per the requirements.