Final answer:
Eugene V. Debs' most likely reason for arrest under the Espionage and Sedition Act was encouraging refusal to join war efforts and fight in the war.
Step-by-step explanation:
The most likely reason for Eugene V. Debs' arrest under the 1917 Espionage and Sedition Act was that his speech may have encouraged listeners to refuse to join war efforts and fight in the war (option B). The Espionage Act was designed to prosecute those who hindered the war effort or assisted the enemy, and Debs' encouragement of draft resistance would have been seen as undermining the war effort. By questioning why working-class men had to fight in a war they had no voice in declaring, Debs' speech went against the government's propaganda campaign and support for the war.