The right answer is B. Expelling the Qing dynasty.
Sun Yat-sen was the leading figure in the national struggle of the people of China. The popular democratic revolution of 1911 was led by him and his party, Tung Meng-hui. This revolution led to the overthrow of Manchu rule in China (The Quing dynasty was the last imperial dynasty in China and ruled from 1636 until the overthrow in 1912) and the establishment of the Republican form of government.