JEE Math Practice Question

If $$f:R \to R$$ is given by $$f(x) = x + 1$$, then the value of $$\mathop {\lim }\limits_{n \to \infty } {1 \over n}\left[ {f(0) + f\left( {{5 \over n}} \right) + f\left( {{{10} \over n}} \right) + ...... + f\left( {{{5(n - 1)} \over n}} \right)} \right]$$ is :

1. A.$${3 \over 2}$$
2. B.$${5 \over 2}$$
3. C.$${1 \over 2}$$
4. D.$${7 \over 2}$$