The basis of the division was social class I believe it was devised between the wealthy, middle, and lower class the lower class included slaves and indebted servants
Movement, Region, Human-Environment Interaction, Location, Place.
Also a mnemonic that I learned today was MR HELP (weird i know) but yeah.
South Africa, Nigeria, and Kenya fall in the following order on the continuum:
A Nigeria
B South Africa
C Kenya