Which of the following is a correct statement?
a. If you attempt to add a record that violates a constraint for one of the table’s columns, only the valid columns for the row are added.
b. A subquery nested in the VALUES clause of an INSERT INTO command can return only one value without generating an Oracle 12cerror message.
c. If you attempt to add a record that violates a NOT NULL constraint, a blank space is inserted automatically in the appropriate column so that Oracle 12c can complete the DML operation.
d. None of the above statements is correct.