Final answer:
The cylindrical stones laid one above the other to form a column or pier are called drums. Arches are composed of wedge-shaped stones called voussoirs, with the keystone at the top. Arches can bear a lot of weight and are used in aqueducts.
Step-by-step explanation:
The cylindrical stones laid one above the other to form a column or pier are called c) Drum. An arch is composed of wedge-shaped stones called voussoirs, with the keystone at the top holding everything in place. Arches can bear a lot of weight and are used in architectural structures like aqueducts.