Which of the following can be used to ensure that once a row has been inserted in table TABLEX, the

Which of the following can be used to ensure that once a row has been inserted in table TABLEX,
the column MAINID in that row cannot be updated?

A.
Define the column MAINID as NOT UPDATABLE.

B.
Define the column MAINID as a PRIMARY KEY.

C.
Define the column MAINID as a FOREIGN KEY.

D.
Define an UPDATE trigger on table TABLEX.