The answer is C: (Rumors) Whispers of doubt filled the empty halls like the reek of rotten eggs.
A mental picture is a representation of the world outside the mind, inside someone´s mind. That is to say, it is an image of the physical world as it is experienced by a subject in reality. Although abstract concepts are, by definition, devoid of specific representations, they can easily be translated into mental pictures that convey their sense and meaning. In the answer above, rumors are linked, through metaphor, to whispers and the smell of rotten eggs, which is a powerful image to represent rumors.
