Which of the following is equal to $\dfrac{1.3.5....(2n-1)}{2.4.6....(2n)}$?

$\dfrac { 1.3.5...(2n-1) }{ 2.4.6...(2n) } \\ \Longrightarrow \dfrac { 1.2.3.4...(2n-1).(2n) }{ { (2.4.6...(2n)) }^{ 2 } } \\ \Longrightarrow \dfrac { 2n! }{ { ((2.1)(2.2).(2.3)...(2.n)) }^{ 2 } } \\ \Longrightarrow \dfrac { 2n! }{ { \left( { 2 }^{ n }n! \right) }^{ 2 } } \\ \Longrightarrow \dfrac { 2n! }{ { \left( { 2 }^{ 2n })(n! \right) }^{ 2 } }$