Question

At the outbreak of both World War I and World War II in Europe, public opinion in the United States generally favored

Answer 1

The answer on the question given above is letter a. remaining neutral.

Based on the European history, World War I is the most destructive.
During the outbreak of both World War I and World War II in Europe, public opinion in the United States generally favored remaining neutral. 
 United States remained neutral although it joined the Allies in 1917.