What important point does this part of olaudah equiano's narrative show about slavery?

I believe the correct answer is - The narrative showed how the interaction among the peoples of Africa and Europe impacted the course of slavery.
In the excerpt, you can see that this slave traveled all over the world while being sold and resold to other slave owners. You can see what he had to go through and what he learned and how he impacted those who owned him. 

Lorna would be the complete subject in this sentence.