已知等差数列\(\left\{ {{a}_{n}} \right\}\)的前\(n\)项和为\({{S}_{n}}\)，\({{a}_{5}}=9\)，\({{S}_{5}}=25\)，则数列\(\left\{ \dfrac{1}{{{a}_{n}}{{a}_{n+1}}} \right\}\)的前\(n\)项和为\((\) \()\)
A. \(\dfrac{n}{2n-1}\)
B. \(\dfrac{n-1}{2n+1}\) C. \(\dfrac{n}{2n+1}\) D. \(\dfrac{2n}{2n+1}\)
