Which country followed a policy of isolationism in the 1930s?
a. france
b. great britain
c. soviet union
d. united states

The correct answer is: "United States"

The policy of isolationism was the approach adopted by the US in foreign policy after WWI and the failure of Woodrow Wilson's internationalism,  specially during the 1930s. Two main reasons: rejecting to use war as an instrument of policy, and the severe economic crisis known as Great Depression, made US citizens reluctant to concern themselves about the growing sucess of fascism in Europe, and led to the enactment of the Neutrality Acts in 1935. These regulations prevented providing economic or military aid to any European country involved in the confrontations.  

b). (sounds as the best answer)