How do you test whether exactly one of two integers is zero, both integers are zero, or neither of the two integers is zero? Select the correct program.
1) Program A: if (a == 0 && b != 0) or (a != 0 && b == 0)
2) Program B: if (a == 0 && b == 0)
3) Program C: if (a != 0 && b != 0)
4) Program D: if (a != 0 || b != 0)