Viscosity and Stokes' law

A tiny spherical oil drop carrying a net charge $q$ is balanced in still air with a vertical uniform electric field of strength $\dfrac{81\pi}{7}\times10^5$ V m⁻¹. When the field is switched off, the drop is observed to fall with terminal velocity $2\times10^{-3}$ m s⁻¹. Given $g=9.8$ m s⁻², viscosity of the air $=1.8\times10^{-5}$ N s m⁻² and the density of oil $=900$ kg m⁻³, the magnitude of $q$ is

Column II shows five systems in which two objects are labelled as X and Y. Also in each case a point P is shown. Column I gives some statements about X and/or Y. Match these statements to the appropriate system(s) from Column II.

As the bubble moves upwards, besides the buoyancy force the following forces are acting on it