Step 1: Understanding the volume change in the rubber ball.
The change in volume of the rubber ball when taken under water is given by the equation:
\[
\Delta V = - \frac{V}{K} \Delta P
\]
Where \( K \) is the bulk modulus, \( V \) is the volume of the ball, and \( \Delta P \) is the change in pressure. The pressure is related to the depth of water by:
\[
\Delta P = \rho g h
\]
Thus, the depth \( h \) is proportional to the given formula:
\[
h = \frac{Kx}{Qg}
\]
Thus, the correct answer is (B) \( \frac{Kx}{Qg} \).