The answer is
B.They could use a similar style of sculptural decoration on all of the exterior and interior walls. C.They could use pleasing proportions for all the parts of the building. D.They could use the same kinds of shapes, colors, textures, and forms as in the natural or man-made surroundings. E.They could add a fountain, gateway, or sculpture that has the lines, forms, colors, or images of the art museum.