The point $\left(5, \frac{\pi}{6}\right)$ can also be represented by which of the following polar coordinates?
(a) $\left(5,-\frac{\pi}{6}\right)$
(b) $\left(-5, \frac{13 \pi}{6}\right)$
(c) $\left(5,-\frac{5 \pi}{6}\right)$
(d) $\left(-5, \frac{7 \pi}{6}\right)$