设数列\(\{a_{n}\}\)的前\(n\)项和为\(S_{n}\)，若\(S_{n}=n^{2}+2n(n∈N^{*})\)，则\( \dfrac {1}{a_{1}a_{2}}+ \dfrac {1}{a_{2}a_{3}}+…+ \dfrac {1}{a_{n}a_{n+1}}=(\) \()\)
A. \( \dfrac {1}{3}- \dfrac {1}{2n+1}\)
B. \( \dfrac {1}{3}- \dfrac {1}{2n+3}\) C. \( \dfrac {1}{6}- \dfrac {1}{4n+3}\) D. \( \dfrac {1}{6}- \dfrac {1}{4n+6}\)
