Well they began considering it because they didn't want another armed revolt like the Americas did. So they peacefully let them leave. Also they let them leave so they could be allies and be valuable trading partners. Also they knew they had enough to deal with like the threat of the cold war bombing. Plus they didn't want India turning to Soviet communism influence. This a basic summary of why they peacefully seceded India and let them become their own country.
Several factors came together. Europe had a population that was on average richer than most other cultures. A very competitive commercial class, ships that were superior than other cultures, developed for the rough North Atlantic, and a number of competitive states rather than a single empire.
The answer to your question is,
C. Breaking up their hoplite formations with cavalry.
-Mabel <3
