ANS:B - square root

In Newton's law range, the terminal velocity VtV_tVt​ of a solid spherical particle falling through a stationary fluid varies as the square root of its diameter ddd. Mathematically, the terminal velocity VtV_tVt​ can be expressed as: Vt∝dV_t \propto \sqrt{d}Vt​∝d​ where ddd is the diameter of the spherical particle. Therefore, the correct answer is: square root