This question was very unpopular among the candidates.  The few who attempted it performed poorly.   They saw it from the point of view of the slave trade mostly.  To score high marks, the candidates were expected to include the following points:

1. states were not self-sufficient and therefore were dependent on other states for exchange of goods;
2. it promoted the spread of European goods between the different Nigerian groups;
3. trade routes actually linked several groups in Nigeria;
4. it brought exchange of cultural ideas;
5. it promoted languages, etc.