A

$\displaystyle\sum\limits_{n=1}^{\infty}\dfrac{2^{n+1}}{3^n}$

B

$\displaystyle\sum\limits_{n=1}^{\infty}(-1)^{n-1}\dfrac{1}{\sqrt{n+5}}$

C

$\displaystyle\sum\limits_{n=1}^{\infty}\dfrac{2n}{n^3+1}$

D

$\displaystyle\sum\limits_{n=1}^{\infty}\dfrac{1}{\sqrt[3]{n}}$