A

\[\left\{\frac{n\pi}{2}/n\in \mathbb{Z}\right\}\]

B

\[\left\{n\pi /n\in \mathbb{Z}\right\}\]

C

\[\left\{(2n+1)\frac{\pi}{2}/n\in \mathbb{Z}\right\}\]

D

\[\left\{(4n+1)\frac{\pi}{2}/n\in \mathbb{Z}\right\}\]

E

\[\left\{(4n-1)\frac{\pi}{2}/n\in \mathbb{Z}\right\}\]