The answer is B. Without the United States, the League lacked the firepower to actually make a huge difference without the individual nations suffering huge consequences. In turn, the League didn't do anything, thus they were ineffective and nothing but a figurehead for democracy and international peace.
The colonists of America had very few opportunities to influence the government of England as they did not have any representation in the British Parliament (which was one of the factors that motivated the Revolutionary War). Because of this, they usually influenced the government through economic measures (ex. by disturbing trade) or through illegal means (ex. rebellions). On the other hand, there are several ways in which people today can influence governments. For example, by writing letters to their representatives, voting in local and federal elections, running for office and lobbying for a cause.
