The kingdoms of ghana and mali became prosperous and powerful because of

during the 20th century, the role of the vice president has evolved into more of an executive branch position. now, the vice president is usually seen as an integral part of a president's administration and presides over the senate only on ceremonial occasions or when a tie-breaking vote may be needed.

hello,

the steamboat is your answer.

it seems like its the only form of transportation on the choices.