The terminal velocity of a liquid drop of radius 'r' falling through air is v. If two such drops are combined to form a bigger drop, the terminal velocity with which the bigger drop falls through air is ( Ignore any buoyant force due to air)

Question

$$(a)\;\sqrt 2\; v \quad (b)\;2\;v \quad (c)\;\sqrt [3] {4} \;v \quad (d)\;\sqrt [3] {2} \;v$$