Why does the author believe that the Mandans were skilled farmersĐoạn văn12/34WhydoestheauthorbelievethattheMandanswereskilled farmersThey developed effective fertilizers.They could grow crops in most types of soil.They could grow crops despite adverse weather.They developed new varieties of corn.Giải thíchChọn đáp án C Giải thích: Dựa vào toàn bộ đoạn 3.