For similarity, in addition to models being geometrically similar to prototype, the following in both cases should also be equal__________________?

A. ratio of inertial force to force due to viscosity
B. ratio of inertial force to force due to gravitation
C. ratio of inertial force to force due to surface tension
D. all the four ratios of inertial force to force due to viscosity, gravitation, surface tension, and elasticity