Why was there tension over who should rule the empire after the death of muhammad ?

Which of these statements describes a long-term impact of european imperialism in africa? a. african countries joined together to present a united front against imperialism. b. europeans paid african countries after colonizing them, offering these new countries a fresh start. c. european powers drew the current borders, splitting ethnic groups among modern countries. d. africans became more loyal to their countries than to their ethnic groups.