Geometry

Question Analysis  
This question involves the special property of spheres: all spheres are similar by definition.
The main focus is recognizing that shape (not size) determines similarity.  

Key Concept Explanation  
All spheres are similar because they have the same shape (perfectly round) and differ only in size.
The ratio of radii (scale factor) can be any positive number.  

Step-by-Step Solution  
The ratio of radii is

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