Answer : 3. "apartment"
Explanation :

An "apartment" is the most appropriate word for a set of rooms forming one residence in a building. The term "apartment" typically refers to a self-contained living space within a larger building or complex, and it is commonly used to describe a single unit within a residential structure. The other options, such as "suite," "villa," and "bungalow," may refer to different types of housing arrangements that may not necessarily involve multiple rooms forming one residence in a building.