Final answer:
Language barriers were likely not discussed among the signs of trade in Western Sudan, which mostly revolved around trade routes, currency exchange, and marketplaces, with salt being a significant form of currency.
Step-by-step explanation:
The question pertains to trade in the Western Sudan and the signs that were not discussed in class among the apparent indicators of trade. Among the options provided: trade routes, currency exchange, marketplaces, and language barriers, it seems that language barriers were less likely to be discussed as a sign of trade. Trade in the Western Sudan, particularly along the trans-Saharan trade routes, primarily involved the exchange of gold, salt, and other goods, with settlements acting as trading centers. Currency exchange was essential as salt acted as a form of currency in this region. Marketplaces were also a sign of trade, as they facilitated the exchange of goods. Trade routes were crucial for linking the distant trading centers of North and West Africa, the Middle East, and Europe. However, language barriers are not typically highlighted as a sign of trade but rather as a potential obstacle to trade that traders and merchants had to overcome to communicate and negotiate effectively.