Why does truman believe it is important to nations preserve their freedom and national integrity in the face of nations “that seek to impose upon them totalitarian regimes”?

Which of the following is an example of nationalism? a. a leader calls on his country's allies to protect his country from a threat posed by a neighboring nation-state. b. one country declares war on another power after that power invades the first country's ally. c. an activist organizes a protest of ethnic minorities in a country to demand that they be given their own country. d. under an alliance, one country promises to defend another country from an attack by a third.