A small spherical monatomic ideal gas bubble (γ = 5/3) is trapped inside a liquid of density ρl (see the figure below). Assume that the bubble does not exchange any heat with the liquid. The bubble contains n moles of gas. The temperature of the gas when the bubble is at the bottom is T0. The height of the liquid is H and the atmospheric pressure is P0 (neglect the surface tension).
As the bubble moves upwards, besides the buoyancy force, which of the following forces is/are acting on it?
(a) Only the force of gravity
(b) The force of gravity and the force due to the presure of the liquid
(c) The force of gravity, the force due to the presure of the liquid, and the force due to the viscosity of the liquid
(d) The force of gravity and the force due to the viscosity of the liquid