Answer: Shouting "Fire" in a crowded theatre.
Step-by-step explanation:
Not all speech is protected by the First Amendment according to the Supreme Court. Speech that is said to have a chance of putting the lives of others in danger is not protected and can lead to a person's arrest and prosecution.
One such speech is yelling "fire" in a crowded theatre where there isn't actually a fire. This can make people panic in an attempt to get away and can cause a stampede where people might get injured or lose their lives therefore it is restricted speech.