What are four items that historians used to find clues? ?

bits of pottery and clay, mounds containing the remains of cities, and ancient writing  

Documents, carbon dating, eye witnesses, fossils

first second and third

explanation:

du boi was considered a radical because he wanted the immediate end for segregation. the biggest different between him and booker t. washington is that, even though washington believed that segregation should be considered illegal, he did not believe at all that a law was needed to keep blacks away from whites and that this would be something natural (to have the races apart) for a long time until society adjusted, while du boi believe that agitation was the only way to end segregation.