A simple question mark, U+003F
<a href="//commons.wikimedia.org/wiki/User_talk:Sarang" title="User talk:Sarang">sarang</a>
2010-12-17
derivated from the shape of the question mark in <a href="//commons.wikimedia.org/wiki/File:Aiga_information_.svg" class="mw-redirect" title="File:Aiga information .svg">Aiga_information_.svg</a>