Which of the Following Statements Is Not Correct About the History

Which of the following statements is not correct about the history of Africa before the twentieth century?

A) The desiccation of the Sahara Desert in the fourth millennium B.C.E. hampered communication between Europe and southern Africa.
B) Africa remained completely isolated from the rest of the world until the Portuguese explorations of the fifteenth century.
C) It was referred to as "darkest Africa" by many contemporary Westerners, who wrongly believed that Africa lacked both civilization and a history.