What is the term used for writing or graphics that are illegally placed on public surfaces?

The term for writing or graphics that are illegally placed on public surfaces is "graffiti." This refers to the unauthorized markings or designs that individuals create on walls, sidewalks, buildings, or other public spaces, often using spray paint or markers. The act of creating graffiti is typically associated with expressing personal views, artistic expression, or marking territory, but it is considered illegal when done without permission.

The other choices represent different aspects of public art or marking. A mural usually refers to a large, decorative painting that is often commissioned or legally sanctioned, distinguishing it from graffiti. Street art encompasses a broader category that might include murals, but it is generally regarded as art created in public spaces and can sometimes be legal. Tagging specifically refers to the stylized signature or logo of a graffiti artist and is often a component of graffiti itself. While tagging can also be illegal, graffiti as an overall term is more comprehensive and includes a wider variety of visual expressions.