The integers 'a' and 'b' can be any, so you can choose a couple and evaluate these expressions to see what you get. For example, we can let a=1 and b=0. For these values, the offered expressions evaluate to ...
A) 3(0) = 0 . . . even
B) 1 +3 = 4 . . . even
C) 2(1+0) = 2 . . . even
D) 1 +2(0) = 1 . . . odd
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<em>Additional comment</em>
These rules apply to even/odd:
odd × odd = odd
odd × even = even
even × even = even
odd + odd = even
odd + even = odd
even + even = even
Then A is (odd)(even) = even; B is (odd)+(odd) = even; C is (even)(whatever) = even; D = (odd)+(even) = odd.
