The correct option is A Chaityas
Chaitya was a rectangular prayer hall with a stupa placed in the centre. The purpose of Chaityas was prayer. The Chaitya was divided into three parts, and had an apsidal ending, i.e, a semicircular rear end. The central part of the hall (also called the nave) was separated from the two aisles by two rows of pillars, The Chaityas also had polished interior walls, semicircular roofs and horse-shoe shaped windows called the Chaitya windows.