Who were the first four caliphs?
a. rulers who had a personal connection to muhammad
b. a group of wealthy traders
c. five gods
d. missionaries to africa

Ifound this on google “the existence of agglomeration economies is central to the explanation of how cities increase in size and population, which places the phenomenon on a larger scale. the concentration of economic activity in cities is one reason for their development and growth.” i hope this you for what your looking for.

Your answer would be a in this question good luck