Review the following declaration.
EXEC SQL BEGIN DECLARE SECTION;

EXEC SQL INVOKE TESTTAB AS test_tbl;
struct test_tbl test;
int new_salary = -1;
EXEC SQL END DECLARE SECTION;
test.salary_i = -1;
Which statement sets the salary column to NULL in the table testtab?

A.
EXEC SQL UPDATE testtab SET salary = 0;

B.
EXEC SQL UPDATE testtab SET salary TO NULL;

C.
EXEC SQL UPDATE testtab SET salary= :new_salary INDICATOR :test.salary_i;

D.
EXEC SQL UPDATE testtab SET salary = :-1;