If n is a positive integer, which of the following must be even?

Question: If n is a positive integer, which of the following must be even?

Solution:
Since n is an integer, it can be EVEN or ODD.
But any integer when multiplied by 2 is even.
For example, 3 × 2 = 6 (even)

The rule is:
EVEN × ODD = EVEN
EVEN × EVEN = EVEN
ODD × ODD = ODD

A) we cant say as it depends if n is odd or even

B) same as (A)

C) Even as n is multiplied by 2

D) It is ODD as EVEN+1 = ODD

E) depends if n is even or odd.