What are some ways that African kingdoms established trade with other civilizations? Select all answers that apply.
a. By beginning trade with other merchants in the Arabian Peninsula.
b. By creating an extensive network of trade routes on the Indian Ocean.
c. By conquering new civilizations to establish trade with the native people.
d. By creating trade laws for other civilizations to trade peacefully.
e. By using the slave trade to extend trade to other civilizations.