How to solve

If $n$ is a positive integer, then. $\underset{n}{lim}{\displaystyle \underset{k=1}{\overset{n}{}}}(\frac{1}{(1+\frac{1}{n}k)})\frac{1}{n},$ can be expressed as

A$.{\displaystyle \underset{1}{\overset{2}{}}}\frac{1}{x+1}dx$

B$.{\displaystyle \underset{1}{\overset{2}{}}}\frac{2}{x+1}dx$

C$.{\displaystyle \underset{0}{\overset{1}{}}}\frac{1}{x}dx$

D$.{\displaystyle \underset{1}{\overset{2}{}}}\frac{1}{x}dx$