Why do you think we do not learn about Emmett Till?

It is true that prior to 1914 the united states often had been disturbed by events in other continents. we had even engaged in two wars with european nations and in a number of undeclared wars in the west indies, in the mediterranean and in the pacific for the maintenance of american rights and for the principles of peaceful commerce. but in no case had a serious threat been raised against our national safety or our continued independence. what is the theme of this excerpt? a. the responsibility for americans to avoid involvement in war.b. america’s history of international involvement.c. a new kind of threat to american security.d. america’s history as a peaceful nation.