Which of these items is typically prohibited in carry-on luggage?

Knives are typically prohibited in carry-on luggage because they are considered potential weapons that could be used to harm passengers or crew members on an aircraft. Regulations regarding carry-on items are primarily focused on ensuring the safety and security of everyone on board. Knives, along with other sharp items, fall under the category of prohibited items due to their ability to inflict injury.

In comparison, books, cosmetics, and clothing are generally allowed in carry-on luggage as they do not pose a threat to safety in the same way that knives do. Understanding the rationale behind these regulations helps passengers adhere to security measures and contributes to a safer travel environment.