Architecture uses forms and space to express cultural values. A. Architects seek to create buildings that are both visually appealing and well suited for human use. B. Both clients and architects are responsible for the mediocre designs of some modern buildings. C. Over the course of the history of building, innovations in material and methods of construction have given architects ever greater freedom to express themselves. D. Modern buildings tend to lack the beauty of ancient stone buildings such as those of Machu Picchu. E. Throughout history buildings have been constructed like human bodies, needing distinct "organ" systems in order to function. F. The discovery and use of the arch typifies the way in which architecture advances by developing more efficient types of structures.