Slavery tolerated because of "necessity" means that you do not really want to do it, but you think you must do it. An example is when you have a farm and you need people to work on it. The trouble behind this scenario is that your farm isn’t making money to pay your farm helpers their proper wages, so you resort to slavery. In this case, you do not need money for salaries because your farm is doing well to keep your slaves clothed and fed.
Slavery affirmed as a "moral right" is when you think it is your right to be the master and the slaves deserves to be slaves.
Harriet Tubman is the most famous conductor. Over a decade she took 19 trips back to the south to guide friends and family to freedom. Every trip was a dangerous trek but it meant freedom for those she cared. Each journey was different and along the years she built up a network of stations owned
Muslim invaders from the Middle East brought their culture, language, and religion to North Africa
Hope this helps