Question

what most affected ancient west african trade?
lack of transportation
natural landforms
limited resources for trade
too many merchants

Explanation:

Natural landforms such as the Sahara Desert acted as both barriers and facilitators (trade routes through oases) in ancient West African trade. Lack of transportation was not a major issue as caravans were used. There were not limited resources for trade (gold, salt etc. were traded). Too many merchants would not negatively affect trade in a fundamental way like landforms did.

Answer:

natural landforms