Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information. A. While American iron makers developed the latest furnaces, African iron makers continued using earlier techniques. B. Africans produced iron much earlier than Americans, inventing technologically sophisticated heating systems. C. Iron making developed earlier in Africa than in the Americas because of the ready availability of carbon and iron ore. D. Both Africa and the Americas developed the capacity for making iron early, but African metallurgy developed at a slower rate.