The correct answer is: Option C. Room's.
Since in the sentence the speaker is referring to the view of the window located in the living room, it is necessary to address the property of the window directly by placing an apostrophe and an s after it.
By placing the apostrophe before the s, it is indicative the view belongs to a window in a single living room. If it was placed after the s, the view would be considered to belong to a window in multiple living rooms.
