What role did trade play in the aztec empire

How do i use this to get the right answer

This term refers to the number of people per unit area (usually a kilometer or a mile). this could refer to the number of people per square mile in a city, a county, a province, a state, or a nation.

Which statement best describes evidence of a mulitcultural mix in east africa? a. because of what he learned during his pilgrimage to mecca, mansa musa was able to build a center of islamic scholarship. b. the traders of ghana brought back with them slaves from the mediterranean who taught the ghana rulers about christianity. c. clans were made up of lineages that were descendants of multiple ancestors from different regions of africa. d. swahili became a language made up of words spoken by traders along the coast of the indian ocean.