The sum of three digit A and each digit of a + 1 is even, so that three digit a has A: 41 B: 43 C: 45 D: 50

The sum of three digit A and each digit of a + 1 is even, so that three digit a has A: 41 B: 43 C: 45 D: 50

0, because one of a and a + 1 is odd and one is even