A

$\displaystyle\lim\limits_{x\to0}\dfrac{x}{x^2+1}$

B

$\displaystyle\lim\limits_{x\to\infty}\dfrac{x}{x^2+1}$

C

$\displaystyle\lim\limits_{n\to-\infty}2^n$

D

$\displaystyle\lim\limits_{n\to+\infty}2^n$