The viscous drag on a small spherical body (moving with slow speed v) is proportional to

Explanation

The correct answer is v. According to Stokes' Law, the viscous drag force experienced by a small spherical object moving slowly through a viscous fluid is directly proportional to its velocity. This is a key concept in fluid dynamics for low Reynolds number conditions, where the flow is laminar. Option A is correct as it correctly reflects this relationship. Options B, C, and D are incorrect because they do not align with the principles of Stokes' Law. Option B suggests a square root dependency, which is not applicable in this context. Option C implies an inverse relationship, which is incorrect, and Option D describes a quadratic relationship more typical of turbulent flows, not the slow speeds described in the question.