Are you speaking about the Greek mythology?
It is (in his attic room)! Words like in, about, outside, between are where prepositional phrases start.
True for example
Box- Boxes
Watch-Watches
etc.
Both the British and Turkish demand the Rosetta Stone.
The British order the French to hand over their treasures.
Both the French army and scholars retreat to Alexandria.
The French scholars hand the Rosetta Stone to the Turks.
The answer is B.
One thing that will help with these kinds of questions is saying each out load to see if they sound right or not