I believe the correct answer is ornate vertical columns.
The Ancient Greek architecture is distinct for its trabeated
system (also known as past and lintel), the use of horizontal beams or lintels
which are borne up by columns. The vertical of the temple support a structure
that rises in two main stages – entablature and the pediment. Ornamentation of
the columns was done in three different styles the Doric style (simple circular
capitals), the Ionic style (use of volutes) and the Corinthian style (floral
ornaments). For example: Temple of Portunus (Ionic style), The Parthenon (Doric
style) and The Pantheon (Corinthian style).
The answer is D. They are realistic and show the American West. The reason is because, well, that is what Albert Bierstadt painted. Albert was from Germany, but he made several journeys to the west and made paintings of what he saw.