Answer:
Explanation:
A: keystone
Keystone is also known as capstone, and it is the stone at the highest point of the arch construction. It is placed as the final piece to lock the construction not to fall, as it is distributing the weight of the arch.
B: voussoir
Voussoir is the name of the whole arched part, including keystone and impost. It is the complete curved element, and the blocks included are most usually made out of stone.
C: impost
The impost is the name for the block that lies at the end of the column, and it is also used for the block that is the start of the arch-shaped element of the arch. It is the base of the voussoir.
