I know that the answer to the question "What might have supported the arches?" is in "From the early 12th century, French builders developed the Gothic style, marked by the use of rib vaults, pointed arches, flying buttresses, and large stained glass windows. It was used mainly in churches and cathedrals, and continued in use until the 16th century in much of Europe. Classic examples of Gothic architecture include Chartres Cathedral and Reims Cathedral in France as well as Salisbury Cathedral in England. Stained glass became a crucial element in the design of churches, which continued to use extensive wall-paintings, now almost all lost.". Can you tell me what it is?
A:
flying buttresses