Những khu vực tập trung đông dân?

Seed plants that lived during the carboniferous impact life on earth today because a. they are the ancestors of all plant life on earth. b. their remains formed coal, which is an important resource. c. they produced fossils that are used to date many geologic events. d. their presence caused oxygen levels to drop, allowing animals to evolve.

Can someone me with this plz? ! i'm putting 20 points on it!

Explain why the rate of urbanisation is in the way it is between developed and undeveloped countries.