During the 1930s the united states followed a foreign policy of isolationism. which is the best example of that policy?

Well, after having to fight with Europe because of the war in 1917, they had unpaid debt and it led throughout the ages, soon after the stock market collapsed. The US became very tired with all the events and isolated themselves. Finally the Hoover Administration set the last tone for the isolationist foreign policy with the Hawley-Smoot Tariff. The big example in all was to get the US back on track economically.  

The answer is c. good luck : )