How did some slave owners try to justify slavery?

The answer is challenging and taxing because arduous means when something is hard and tiring and the excerpt provides clear detail why that's the answer

It developed as a reaction to the impact of european colonialism in africa on peoples of african descent. in the  mid-20th century, activists in africa adopted pan-africanism as a rallying cry for independence from colonial rule. some african pan-africanists sought to unite the continent as one independenthope it was useful