JEE Math Practice Question

If $${U_n} = \left( {1 + {1 \over {{n^2}}}} \right)\left( {1 + {{{2^2}} \over {{n^2}}}} \right)^2.....\left( {1 + {{{n^2}} \over {{n^2}}}} \right)^n$$, then $$\mathop {\lim }\limits_{n \to \infty } {({U_n})^{{{ - 4} \over {{n^2}}}}}$$ is equal to :

1. A.$${{{e^2}} \over {16}}$$
2. B.$${4 \over e}$$
3. C.$${{16} \over {{e^2}}}$$
4. D.$${4 \over {{e^2}}}$$