A

$\displaystyle\sum_{n=1}^{\infty}(-1)^n\dfrac1{\sqrt n}$

B

$\displaystyle\sum_{n=1}^{\infty}(-1)^{n-1}\dfrac n{3^{2n-1}}$

C

$\displaystyle\sum_{n=1}^{\infty}(-1)^n\sin\dfrac\pi n$

D

$\displaystyle\sum_{n=1}^{\infty}(-1)^{n+1}\dfrac{2^{n^2}}{n!}$