will be generated by attempting which of the following?

The error message
Index or primary key cannot contain a Null Value.
(A) A user tries to enter a record in the table Countries that doesn’t contain data in the
primary key.
(B) A user tries to add a record to a table that is related to the Countries table, and that
record contains a foreign key value that does NOT correspond to a primary key value in
the Countries table.
(C) A user tries to enter a record in the table Countries with the same primary key as
another record.
(D) A user tries to request a joined table using LINQ.

(A) A user tries to enter a record in the table Countries that doesn’t contain data in the
primary key.