Final answer:
A trader's boss might be secretive to avoid becoming a target in the perilous trading environment of the medieval Sahara, where gold and salt were exchanged across vast networks, and to maintain exclusive access to valuable resources.
Step-by-step explanation:
The boss in a medieval trans-Saharan trading operation may have been secretive due to various reasons related to security and trade advantages. Moving valuable commodities such as gold and salt across the Sahara was fraught with risks, including banditry and political instability.
Trusting an assistant to conduct face-to-face transactions minimized the risk of the boss becoming a target and helped protect the location of precious resources, like the gold towns controlled by the Wangarans, whose secrecy assured their exclusive access to these resources. Furthermore, the spread of Islam in the region established a level of trust and legal framework amongst Muslim traders, which could have offered a degree of assurance even without direct contact by the trading boss.