A bumpkin   went to a big city for the first time. He went into an office building and saw a short and fat woman stepped into a small room. After her, the door closed and the light on the top flashed. After a while the door opened slowly, a young beautiful modern girl walked out of the small room. The bumpkin opened his eyes wide in surprise. He said to himself in a low voice, "What a pity! I haven't brought my wife here!" The room he saw was perhaps   _  .
an office a toilet a lift a helicopter