The correct answer is false.
It is false that in Schenck v. U.S., the Supreme Court ruled that the Espionage Act was unconstitutional.
What the United States Supreme Court ruled on this case was that freedom of speech could be suppressed or limited if it represented a risk for the national security of the country. The decision was made on March 3, 1991.
The context is that the United States decided to enter World War I, and the government passed the Espionage Act that prohibited any act against the United States' interests and any action that favored the enemy.