Answer:
C. The right to free speech.
Step-by-step explanation:
In the Schenck v. United States case, the Supreme Court limited the right to free speech by establishing the "clear and present danger" test. The court held that speech that presents a clear and present danger to the public or incites unlawful action is not protected under the First Amendment. This case involved Charles Schenck, who was charged with violating the Espionage Act of 1917 for distributing anti-draft leaflets during World War I. The court ruled that his speech posed a clear and present danger to the country's war effort and upheld his conviction, establishing a precedent for limiting free speech rights in certain circumstances.