Frame buffer size $= 640 * 480 = 307200$ pixels
Access time = $200$ nanoseconds$/$pixel $= 200*10^{-9}\space$ sec$/$pixel
No.of pixels accessed in $1\space sec$ $= \frac{1}{200 * 10^{-9}\space sec /pixel} = 5$ x$10^6$
Refresh rate $= \frac{access\space rate}{frame\space size}$ $= \frac{5 *10^6\space pixels/sec}{307200\space pixels}$
$= 16.27 $ per sec.
So, the answer is $(1)$.