World war 1 brought increased immigration to the united states from which country

Immigration to the US during WWI led to an average of 1 million immigrants per year, since the US policy of "open door” immigration did not establish a limit on the number of people who could enter the country. Masses of immigrants who escaped the hardships of this long-lasting war came from European countries such as Italy, France, Germany, Britain and Russia. Besides, many refugees came from Bulgaria, Greece, Romania, Serbia, and Turkey, as well as Jews who fled for their lives from anti-Semitic feeling throughout eastern Europe. It is important to state that many immigrants enlisted in American military forces and served the US during the development of WWI.

the answer would be c