Final answer:
The example of an ancient Arabian state trading on the East African coast provides evidence of the significance of trade and the emergence of commercial city-states.
Step-by-step explanation:
The example of an ancient Arabian state that traded extensively and controlled territories on the East African coast can best be used as evidence of the interconnectedness and importance of trade in the East African region during ancient times. The trade networks established by the Arabian state helped facilitate the exchange of valuable raw materials such as spices, tortoise shells, coconut oil, ivory, gold, and slaves. The emergence of commercial city-states along the coast in the 10th century CE further indicates the economic significance and competition for control over trade routes in the region.