I’m sorry for the intrusion, but since I did this mock test a couple of weeks ago and still remember this particular question, I thought I would add my two cents, if you don’t mind.
I think the most confusing thing about it is the way the elevator is depicted in the illustration: namely, as a separate door near the stairway in the middle of the building. I’m not sure how elevators are built in Japan, but where I’m from and where I’m living now, they are usually placed inside the building. So, that was a bit confusing at first.
But once you identify the elevator, the only logical answer to the question is indeed answer number 2. The room is situated far from the elevator and it’s neither on the second, nor on the third floor. Which only leaves the room to the right on the fifth floor, since the other one is situated close to the elevator 
Woah, never would have guessed, since to me, this thing on the left kind of looked detached from the building.