During the first decades of the twentieth century, the British Empire had a population of about 458 million people and about 33,700,000 km², which meant approximately a quarter of the world's population and a fifth of the land area. This makes it the first largest empire in history. The culminating period of the empire took place for about a hundred years (the so-called imperial century, developed between 1815 and 1914), through a series of expansion phases related to trade, colonization and conquest, as well as periods of diplomatic activity . Probably, the point of maximum imperial boom can be between 1880 and 1930.
During the colonial period, Britain controlled "Swaziland" although it should be noted that the British Empire had many other colonial holdings in Africa during this time as well.
Easy answer. It is D. Only problem was that though the Woodrow Wilson proposed the idea the US never joined therefore no country actually listened to the decisions the LoN made.