Final answer:
The excerpt from Ibn Battuta suggests that copper was a significant commodity in the Songhai Empire's trade, used as a medium of exchange for a variety of goods. Hence, the correct answer is option B.
Step-by-step explanation:
The conclusion about trade in the Songhai Empire that is supported by the excerpt from Ibn Battuta's description of his journey to Taghadda is that copper was a significant commodity in the trade of the Songhai Empire. Battuta notes that copper bars served as a medium of exchange, indicating its crucial role in the Songhai economy.
The thin bars were used to buy everyday items like meat and firewood, while the thicker bars were exchanged for more valuable items such as slaves and food staples like millet, butter, and wheat. This use of copper for trade purposes points out its significance in the Songhai Empire’s economic system.