C. Opportunity cost
This is the opportuntiy that they lost. it costed them. Thus, opportunity cost for another opportunity.
I guess I'll just write about people, since it'll be the fastest for me.
1. George Washington, the very first president of the United States of America. He was a great leader, and he helped bring an entire nation together with the help of his allies and supporters.
2. Frederick Douglass, a runaway slave and the man who most likely contributed to the Black Power movement the most. He gave powerful speeches everywhere, and thanks to that he helped make all black men and women free from slavery. Not equal, but they were free.
3. Rosa Parks. She boycotted against the way blacks were treated, and, probably the most memorable thing she did, she refused to sit in the back of a bus, where the blacks were forced to sit, and that brought more people to fight for black rights.
Answer:
killing thousands and millions of people in a war or even in many things.
Explanation:
The first step historians take as part of the historical thinking process is to pose the historical question and establish relevant background about the topic. Thank you for posting your question. I hope this answer helped you. Let me know if you need more help.