Which two statements are true regarding a PL/SQL package body?

Which two statements are true regarding a PL/SQL package body? (Choose two.)

A.
It cannot be created without a package specification.

B.
It can be changed and recompiled without making the package specification invalid.

C.
It can contain only the subprograms defined in the package specification.

D.
It cannot invoke subprograms defined in other packages.