The answer is 4. They protected Muslim communities. The Axum Kingdom gave protection among Persian and Muslim merchants. It also supported the trade by opening ports that would become a trading African location in Asia. In other words, Axum was open to economic trade with other countries and even let the traders live in their communities.
Source: https://howellworldhistory.wordpress.com/quarter-4/unused/kingdoms-and-trading-states-of-east-africa...