Which of the following amendments to the U.S. Constitution relates to freedom of speech?

The First Amendment to the U.S. Constitution is directly related to freedom of speech. It guarantees individuals the right to express themselves freely without government interference. This amendment encompasses not only verbal communication but also symbolic speech, such as protests and demonstrations. The significance of the First Amendment in protecting free speech is foundational to the democratic principles of the United States, as it allows for diverse opinions and open discussion, which are essential for a healthy society.

The other amendments listed do not pertain to freedom of speech. The Second Amendment focuses on the right to keep and bear arms, the Fifth Amendment addresses rights related to legal proceedings, including protection against self-incrimination, and the Sixth Amendment ensures rights related to criminal prosecutions, such as the right to a fair trial. Each of these amendments serves a distinct purpose within the Constitution, but it is the First Amendment that explicitly secures individuals' rights to freely express their thoughts and opinions.