Answer:
C: B+C
Step-by-step explanation:
A-B is even so A and B are either both even or odd.
A-C is odd so one is even and the other is odd.
Because A is common to both cases B and C have to be of different parities.
In answer A, B, and D we are not sure of the parity of the numbers.
However, in answer C we know that B and C are of different parities, and and even plus and odd is odd.