The answer is a. "Sensory detail".
In "The Pit and the Pendulum," the narrator finds himself tied down flat, with a sharp pendulum slowly swinging downwards towards him.
He finds that he is unable to untie himself.
Earlier, he was given food, containing meat, and that food is within his reach, though he is tied down.
He finds rats are in the cell with him, so he devises a plan.
He takes the meat from his dish and rubs it all over the ropes tying him down. The rats then jump up onto him and begin gnawing on the ropes. Eventually, he is able to split the chewed ropes and free himself.
Remark
Let's begin with the theme. What is the theme of this passage, exactly? Four people -- five if you include Dr. Heidegger -- are sitting around a circle bemoaning the fact that they have lost something not granted to anyone. They have lost their second youth. They have swallowed some water which gave them their youth only for a fleeting moment (it seems to them), and they mourn the passage of time that grants them no more youth that they had been living in for some short period.
The four felt that way. Only Dr. Heidegger seemed to have learned something that told him that he should be careful what he wished for: he might actually get it.
We have two themes then. We have 4 who wished for their youth back and we have one who didn't want any part of it. I think we have to cover both.
The best detail for those wanting it is the old woman who apparently got her youth back and she was incredibly beautiful. Now her hands are skinny and likely wrinkled. She puts those hands to her face and wishes herself to be dead because she despises the fact that she is old (and likely all her friends are dead and she is condemned to a life of weariness. I speculate, but is certainly unhappy about the aging process). She mourns that it is over so quickly. They all do. That's sentence 3.
Only Dr. Heidegger seems to understand that they got something they should never have received in the first place. The yellow sentence beginning with "Well I bemoan it not, ... " reflects his point view as well as anything. That's sentence 5.
