I believe the correct answer is piers and flying
buttresses.
Builders of Gothic cathedrals reinforced the walls
of their architecture from the outside with piers (such as bridges or arcs) and
flying buttresses (a type of buttress which is composed of an arched structure
that extends from the upper portion of a wall to a pier) in order to provide
the lateral support.
I don’t really know, but I think it is B.
