Translation:It is a room.
As far as I know, 部屋 (heya) usually refers to a bedroom. (My dictionary even offer "sumo stable" as an alternative to "room".)
A room in general, depending on the context, can be 空間 (kuukan) or 室 (shitsu), though the latter is usually used more as a suffix like in "classroom" = 教室 kyoushitsu
As I mentioned in an earlier comment, to my understanding 部屋 usually refers to a bedroom, so yes, all of your suggestions are possible (though "the room" seems more unlikely, without extra information in the Japanese sentence).
Apartments/studios, well, real estate in general, is quite small/space-efficient in Japan, so students' apartments are likely to be single rooms, with the kitchen, dining living, bedroom, etc. all sharing the one room. As such, someone's apartment is generally referred to using 部屋; also because アパート typically refers to the entire apartment building, rather than a specific room.