Read this excerpt from president roosevelt's four freedoms speech:
it is true that prior to 1914 the united states often had to be distributed by events other continents. we had even engaged in two wars with european nations and in a number of undeclared wars in the west indies and the mediterranean and in the pacific for the maintenance of american rights in for the principles of peaceful commerce. but is no case had a serious threat being raised against our national safety or our continued independence

what is the theme if this excerpt?

a. america's history as a peaceful nation
b. the responsibility for americans to avoid involvement in war
c. a new kind of threat to american security
d. america's history to international involvement