Which sentence is the most formal in dictation and style

Aids is growing fastest in the poorest countries of africa. these nations don’t have enough doctors, medical labs, or money for medicine. a recent study showed that only a small percentage of hiv-infected children in africa are getting any medical treatment at all. what central idea is emphasized in both sources? the hiv/aids epidemic in africa is serious. the hiv/aids epidemic in south africa is serious. the hiv/aids epidemic among african children is serious. the hiv/aids epidemic among south african children is serious