If m and n are distinct natural numbers, then which of the following is/are integer/integers?
1. `(m)/(n) +(n)/(m)`
2. `mn ((m)/(n)+(n)/(m)) (m^(2)+n^(2))^(-1)`
3. `(mn)/(m^(2)+n^(2))`
Select the correct answer using the code given below.

Options

A. 1 and 2
B. 2 only
C. 2 and 3
D. 3 only