What effect did the sinking of the Lusitania have on World War I?

AIt almost ended the war prematurely.
BIt confused Britain as to whether or not the United States was its ally.
CIt outraged many Americans and made it increasing difficult for the United States to remain neutral.
DIt outraged many Germans and made the German government consider a declaration of war against the United States.

Verified Answer :

The primary effect that the sinking of the Lusitania had on World War I was that "C. It outraged many Americans and made it increasing difficult for the United States to remain neutral," since many Americans were killed.