Choose the word which is different from the rest.

The answer is C. Poster.

A sketch is a rough drawing or outline of something. Paper is a thin, flexible material made from cellulose fibers. A diagram is a drawing that shows the structure of something or how something works. A poster is a large printed advertisement or notice.

A poster is different from the other options because it is the only one that is specifically designed to be displayed in public. A sketch, paper, and diagram can all be used for a variety of purposes, but a poster is typically used to promote something or to provide information to a large audience.