Detailed Instructions: Generate a question which can yield the answer mentioned in the input. Generated question must be answered by the answer provided in input, without using any extra knowledge.
Problem:Context : Culham Bridge was built of stone between 1416 and 1422 to replace an ancient ford called Culham Hythe by a religious body known as The Brotherhood of Christ (later Christ's Hospital) who subsequently looked after its upkeep.
Answer : stone
Solution:
What is the surface of Culham Bridge made of?