How many humant are on earth?

Which physical feature minimizes population density in northern africa?

What is significant about official languages in russian republics? why would it matter?

Which of these is not a criticism of the concentric zone model? it does not accurately describe cities after the rise of suburban development. it only applies to cities that grew after the development of the automobile. it assumes that inner-city areas will always be repurposed instead of abandoned. it places too much importance on the traditional central business district.