If n is even, which of the following cannot be odd?
A
n+3
B
3n+1
C
n2-1
D
2(n+3)
Correct Answer: 2(n+3)
even = odd = odd ∴ n + 3 = odd odd × even + 1 = odd ∴ 3n + 1 = odd even2 - 1 = even - 1 = odd ∴n2 - 1 = odd 2(even + odd) = 2 × odd = even ∴ 2 (n + 3) = even