Frank Lloyd Wright added beauty to this building in the following ways; designed it to be in harmony with its environment, meant to stick out from landscape and be in contract to nature, used horizontal rectangles to unite his building with the earth, cantilevered the floors and roofs so they float over a cliff and waterfall

designed it to be in harmony with its environment

cantilevered the floors and roofs so they float over a cliff and waterfall

Explanation:

The house was built on a waterfall but so that the waterfall becomes part of the house, it was Wright's philosophy to respect nature and make buildings that will not stand out but will be an integral part of the terrain and landscape. Wright set the stairs descending directly from the living room onto the water cliffs, and the sound of the waterfall would fill most of the house, creating a cozy atmosphere.It is also characterized by an open space filled with light.

It's most likely choice a, it makes the most sense in my opinion.