If a record variable contains a NULL value for a field, how is it treated if it's used in an UPDATE statement? a. The associated column is unaffected. b. The UPDATE action fails. c. The associated column is set to NULL. d. A record variable can't hold a NULL value. When should you use the %ROWTYPE attribute in creating a record variable? a. when using most of the columns from a table b. when using only a small portion of the columns from a table c. whenever a record variable is created d. none of the above