$A$ small steel sphere of mass $m$ is falling vertically through a viscous liquid with a constant speed $v$. Which row in the table correctly describes the changes with time in the kinetic energy and gravitational potential energy of the sphere?

• A
  constant and equal to $\frac{1}{2} mv^2$ || decreases at a rate of $mgv$
• B
  constant and equal to $\frac{1}{2} mv^2$ || decreases at a rate of $(mgv - \frac{1}{2} mv^2)$
• C
  increases at a rate of $mgv$ || decreases at a rate of $mgv$
• D
  increases at a rate of $mgv$ || decreases at a rate of $(\frac{1}{2} mv^2 - mgv)$