He ended slavery in america
The US tried to stop the spread of communism by the Marshall Plan (giving economic aid to devasted countries), by the Berlin Airlift, by the creation of NATO and by helping form the United Nations.
It demonstrates the idea of fulfilling your destiny, and following your dharma. Arjun makes the decision to fight and thus completes his duties, virtues and destiny. This is framed as the right decision, doing what you are supposed to do.
The Great Depression happened
the answer is C. establishing a limit to the number of terms a senator can serve...... :)