Answer:
4. Indian Ocean
5.The language dates from the contacts of Arabian traders with the inhabitants of the east coast of Africa over many centuries. Under Arab influence, Swahili originated as a lingua franca used by several closely related Bantu-speaking tribal groups. ... Standard Swahili is based on the kiUnguja dialect.
6.The establishment of trade affected the coastal cities by making them wealthier and bigger. They also were rivals to each other. ... It suggests that the people of East Africa were wealthy and were able to trade valuable things to other societies.
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