What is notable about the materials used in Ai Weiwei's 'The Bridge Without a Name' at the Middelheim Open Air Sculpture Museum?

A. He recycled a small bridge that was already present at the sculpture park and added his own touches to it
B. He used a combination of recycled and new materials to create the bridge
C. He used only new materials to construct the bridge from scratch
D. He used materials that were specifically imported from China to create the bridge
Answer: 