Gustav Klimt's controversial poster for the first exhibition of the Vienna Secession featured Greek mythological figures that represented the struggle between the Secession and the established art world.

relief sculpture - images are set against a flat background.

a coin is a good example: the inscription, the date, and the figure are slightly raised above a flat surface. the ancient egyptians sometimes carved figures into a flat surface.  

pro: they take significantly less time to make and do not require as much tools or skills as free-standing

cons: not nearly as realistic, as it is not fully 3-d, and does not have the details that a free-standing one does.

freestanding sculptures (also called  carved in the round) are not attached to any  background.   they are 3-dimensional  and fully rendered.

answer: brancusi's  bird in space  is a sculpture series. the sculptures represent movement rather than an actual bird. john audubon's  wild turkey  is literally a picture of a wild turkey, so his is the most effective in doing so. 

explanation: