3. Let the two legs of the right triangle $\triangle A B C$ have lengths 5 and 12, respectively. We draw two arcs, one centered at $A$ with a radius of 12, and the other centered at $B$ with a radius of 5. These arcs intersect the hypotenuse at $M$ and $N$, respectively. The length of the line segment $M N$ is
(A) 2, (B) $\frac{13}{5}$;
(C) 3 ; (D) 4 ;
(E) $\frac{24}{5}$.
3. From $\triangle A B C$ being a right triangle, we get $A B=13$. Additionally, $B N=B C=5, A M=A C=12$, so $B M=A B-A M=1, M N=B N-B M=4$.
(D) True.