Final answer:
Prefabricated building materials are the innovation that allowed for the construction of unique structures like the Guggenheim Museum Bilbao, providing precision and accommodating complex designs.
Step-by-step explanation:
The innovation that made possible structures like the Guggenheim Museum Bilbao was B. Prefabricated building materials. With advancements in modern architecture, the use of computer-aided machines allowed for the prefabrication of building components, integral to the creation of unique and complex structures. These components are accurately and efficiently produced, which when assembled on-site, contribute to innovative architectural forms like those of Frank Gehry's Guggenheim Museum Bilbao. This museum features distinctive curvilinear forms and materials such as titanium, which were possible through these modern building techniques. Using prefabricated building materials ensured precision, reduced human error, and accommodated the museum's unique design which includes smooth stone, glass, and folding titanium curvatures that define its avant-garde aesthetic.