To keep up with demand, how did African slave traders obtain more enslaved people?
They took prisoners of war and raided villages.
They stopped selling enslaved people to the Middle East.
They traded goods with Africans on the west coast.
They improved conditions on slave ships to help people survive.
"They took prisoners of war and raided villages" would be the best option from the list, since European demand for slaves dictated that they needed to increase their inventory by any means possible.