Answer:
[tex] \frac{2\pi}{ 3} = 120 \: degrees[/tex]
[tex]arc PR = 2\pi.r( \frac{120}{360} )[/tex]
[tex] = 2\pi(8) \times \frac{1}{3} [/tex]
[tex] = \frac{16\pi}{3} [/tex]
option D