Your Answer would be D, Hope This Helps
Multiple choice? if you do then pass it to me so I can see if I can help you okay.
c) spread of communism in America
"The following month, Germany sunk four more U.S. merchant ships. ... On April 6, 1917, the United States entered World War I. Get a firsthand look at how a new breed of weapons like WMDs, submarines, armored tanks and air attacks changed modern warfare forever in WWI: The First Modern War"