Which statement is true about combined scaling using both N and D according to the provided material?

• A. Combined scaling uses both N and D accordingly
• B. Combined scaling uses only N
• C. Combined scaling uses only D
• D. Combined scaling ignores both N and D

Answer: (B)

In this material, combined scaling is represented by a single factor that captures the net effect of the scaling’s influence on the system. The idea is that the overall similarity is achieved with one dominant scaling parameter, rather than applying two independent factors. Here, that sole factor is N, so the combined scaling uses only N and does not apply D separately. This aligns with the way the material defines the scaling relationship, where any effect that D might have is already encompassed within N or cancels out in the similarity equations. Using D separately would contradict that defined approach, and suggesting that neither parameter is used would fail to maintain the required similarity.