A large sleeping-room with many beds

Answer: Option B

One word substitute is Dormitory.

Bedroom: a room for sleeping in.
Dormitory: a large bedroom for a number of people in a school or institution.
Hostel: an establishment which provides inexpensive food and lodging for a specific group of people, such as students, workers, or travellers.
Basement: the floor of a building which is partly or entirely below ground level.