Look at the diagram above. Label parts of the arch: A, B, and C.

Answer:

Explanation:

A: keystone

The keystone, also referred to as the capstone, represents the stone positioned at the apex of the arch's structure. Serving as the last component, it secures the assembly by evenly distributing the arch's weight to prevent collapse.

B: voussoir

The term voussoir designates the entire arched section, which comprises both the keystone and the impost. It encompasses the full curvature, with the blocks typically crafted from stone.

C: impost

The impost describes the block situated at the top of the column, and it also refers to the block initiating the arch's curved structure of the arch. This serves as the foundation for the voussoir.