The correct answer is B) using contextualization.
The historian's conclusion is an example of using contextualization.
As we see in the example, the historian is in learning the use Romans did of the ancient Roman Colosseum. This was a kind of today arena where trained fighters battled one another for amuse people and entertainment. The participants were gladiators, slaves who were forced to fight to the death with other people and even wild animals. So the historian can't understand how any person would enjoy or even tolerate watching such things. He concludes that ancient Roman culture must have been significantly more tolerant of violence and slavery than modern American culture. He reached this conclusion by using contextualization, which means, having contemplated all the circumstances and factors that surround the moment in history.