The correct answer is: Option C) Give hints about the characters of Dr. Heidegger's guests.
<em>Withered, melancholy, </em>and <em>foul </em>were words to describe the characters' appareances and personalities, as they were later explicitly revealed to be very old people - and they indeed turn out to be cynical and senile elders who yearn to retrieve their youth -. This description is meant to give the reader a visual idea of how the characters should look like, and predict how they would behave throughout the story based on a brief introduction.