Choose all the right answers. Why do plants need nitrogen?

for food
for energy
to make protein
to make new cells

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.