The correct answer in this case is liberalism.
Socialism is the opposite as it entails (Among other things) the idea of fast changes, if need be with revolution. Neither does utilitarianism talk about social progress through reform.
Libertarians talk exactly about what the question is about; one of the main tennets of liberalism is that they prefer and would like to witness social change through reforms.
Since 1990 the Japanese economy has slowed down. It is known as the lost decade, or lost Two Decades/ 20 years (initally people hoped it would be over after 10 years), where the GDP and real wages have dropped.
I believe A and C are correct.
American involvement in Vietnam
Longest war in American history divides the nation
D. Because Martin Luther King never ran for president, The Lincoln Memorial Was built in 1922, and Negro slaves were already freed because of the thirteenth amendment