1. (10 points) If $\frac{2013 \times 2013}{2014 \times 2014+2012}=\frac{\mathrm{n}}{\mathrm{m}}$ (where $m$ and $n$ are coprime natural numbers), then the value of $m+n$ is ( )
A. 1243
B. 1343
C. 4025
D. 4029
【Analysis】 $\frac{2013 \times 2013}{2014 \times 2014+2012}=\frac{2013 \times 2013}{(2013+1)^{2}+2013-1}=\frac{2013 \times 2013}{2013^{2}+2 \times 2013+2013}=$ $\frac{2013}{2016}=\frac{671}{672}$, so $n=671, m=672, m+n=1343$.
【Solution】Solution: $\frac{2013 \times 2013}{2014 \times 2014+2012}=\frac{\mathrm{n}}{\mathrm{m}}=\frac{2013}{2016}=\frac{671}{672}$, so $n=671, m=672, m+n=1343$.

Therefore, the correct choice is: B.