Answer:
A historian can study ancient Roman culture to learn about attitudes of Roman toward slavery and violence.
Step-by-step explanation:
The historian has a difficult time understanding how any person would enjoy, or even tolerate, watching such a thing where slaves were forced to fight to the death with other people and even wild animals just for spectators' entertainment.
To better understand the Colosseum, a historian can study ancient Roman culture to learn about the attitudes of Roman toward slavery and violence.