Helped to cause an economic boom in Oklahoma during the 1920s. The discovery of large deposits of
A. coal
B. oil
C. copper
D. silver

Over time, historians have changed the ways they study the past because they have: o a. emphasized the study of oral history passed down in communities for generations. o b. started to explore history through the perspectives of many different groups. c. focused on uncovering archaeological evidence rather than analyzing documents. d. largely abandoned studying comparative and cultural history in favor of microhistory.