challenge: What is the purpose of using abbreviations CG-1, CG-2, and CG-3 in the context of compactly generated spaces?
  
  A. To classify compactly generated spaces based on their topological properties
  B. To express results in a more concise way by referring to the three commonly used definitions
  C. To denote the number of dimensions in a compactly generated space
  D. To distinguish between different types of compactly generated spaces
  Answer: 