A container filled with viscous liquid is moving vertically downwards with constant speed\[3{{v}_{0}}\]. At the instant shown, a sphere of radius r is moving vertically downwards (in liquid) has speed\[{{v}_{0}}\]. The coefficient of viscosity is\[\eta \]. There is no relative motion between the liquid and the container. Then at the shown instant, the magnitude of viscous force acting on sphere is

• A. \[6\pi \eta r{{v}_{0}}\]
• B. \[12\pi \eta r{{v}_{0}}\]
• C. \[18\pi \eta r{{v}_{0}}\]
• D. \[24\pi \eta r{{v}_{0}}\]