Which one of the following statements on similitude is correct ?

To achieve dynamic similarity between the model and the prototype, there need not be any geometric similarity.

For kinematic similarity between the model and the prototype, the ratios of forces between the model and the prototype should be the same.

For dynamic similarity between model and prototype in a compressible flow system, the Weber numbers must be the same.

For dynamic similarity between the model and the prototype, the ratio of forces must be the same.