Which of the Following Statements About the Rise of Trade

Which of the following statements about the rise of trade is correct?

A) Trade was aided by the establishment of settled communities, which typically locally lacked some needed goods.
B) Trade initially emerged as groups who migrated to the Americas sought to sustain cultural and trade contacts with groups in northeast Asia.
C) Trade was limited by the lack of pack animals that could cross long distances in arid conditions.
D) Trade emerged after about 500 BCE, when settled communities had reached large populations.