A student sees the top edge and the bottom center C of a pool simultaneously from an angle θ above the horizontal as shown in the figure. The refraction index of water which fills up to the top edge of the pool is 4/3. If h/x = 7/4 then `cos theta` is
A. `(2)/(7)`
B. `(8)/(3sqrt(45))`
C. `(8)/(3sqrt(53))`
D. `(8)/(21)`
