Criticism of the war at home was effectively silenced by

d. the Espionage and Sedition Acts.

Explanation:

The espionage act of 1917 was passed by the government of the United States of America to curb anyone interfering with activities of the armed forces. It was a breakthrough to eliminate the anti-war voices. The Sedition Act was passed next year was further development of the Espionage Act in which harsh penalties were allotted for those who question the government's foreign policy or military actions.