Alexander the Great destroyed the city of Thebes because he wanted to send a message to the other Greeks that were thinking of revolting like Thebes did. Thebes and other Greek city-states had a pact with Phillip II, Alexander's father, king of Macedonia, that they would be a part of Macedonia. When Phillip died and Alexander took over Macedonia, the Greeks did not want to bow to a 'child' (a 20 year old). Also it had been rumored in the cities that Alexander was dead and it was the perfect time to revolt. That is the reason Alexander the Great destroyed the city of Thebes.
The correct answer here is the option C.
In order to keep the fragile balance of power in the period before the World War I, countries entered alliances with one another. So for example, France, Russia and the Great Britain were in one alliance and the Germans and Austrians in another. If one country entered a war the other were obliged to go to their aid. That is how the World War I escalated.
