Final answer:
A rib against a wall, parallel to the longitudinal axis of a rib vault in architecture, is known as a wall rib. This feature is significant in Gothic architecture, where it provides stability and support for the vault's weight.
Option B wall rib is correct.
Step-by-step explanation:
In architecture, a rib against a wall, parallel to the longitudinal axis of a rib vault, is known as a wall rib. A wall rib supports the webbing of a vault and transmits the weight to the wall it is attached to. The ribbed vaulting is a feature, especially noted in Gothic architecture, where its design allows for greater height and stability of the structure. The development of the pointed arch and ribbed vaulting can also be seen in late-Romanesque buildings before it became a defining element of the Gothic style.
Ribbed vaults enhance the strength and stability of the building by distributing the weight of the ceiling across a series of ribs, rather than concentrating it on the walls. This structure became crucial as Gothic churches reached new heights and large openings were made for stained glass, necessitating a strong framework to manage the outward forces and heavy stone loads. Thus, the correct answer to the student's question is B. Wall Rib.