ANS:B - Newton

Viscosity, which is a measure of a fluid's resistance to flow, was described by Sir Isaac Newton. He formulated the concept of viscosity based on his observations of fluid behavior, which led to the development of Newton's law of viscosity. According to Newton's law of viscosity, the shear stress between adjacent fluid layers is directly proportional to the velocity gradient (rate of change of velocity with respect to distance) in the direction perpendicular to the flow. Therefore, the correct answer is Newton.