The correct options are
A A section called Viharas were used as residences for the monks.
B A section called Chaitya was the hall for worship.
C There would usually be a stupa at one end of the Chaitya Hall.
The monks used the Viharas as residences. The Chaitya was a hall used for worship, usually with a Stupa at one end. The other characteristics of a Chaitya were- a large window above the decorated main door and long rows of pillars in the halls.