When a Small Spherical Rock of Radius R Falls Through

Multiple Choice

When a small spherical rock of radius r falls through water, it experiences a drag force (a) is its velocity and "a" is a constant proportional to the viscosity of water. From this, one can deduce that if a rock of diameter 2 mm falls with terminal velocity, "v," then a rock of diameter 4 mm will fall with terminal velocity

A) 2 v.
B) 4 v.
C) v / 4.
D) v.
E) v / 2.