Read the following passage and questions, then choose the right answer from options, the answer should be one of A, B, C, D.

<passage>:
"These donors were dead, but you can be thankful we had parts of their brains available." Crander delved into the file and came up with a sheet. mind in a sound body, but Dan Merrol had too much of one—and also too much of the other! sat up. "They said you were Dan Merrol at the hospital, but they must "But I should know, shouldn't I?" "Of course, but...." He did some verbal backstepping. "It was a "My name is Dan Merrol." like Dan Merrol. "They told you that too." She was wrong again, but it was probably wiser not to tell her how he knew. No one had said anything to him in the hospital. He hadn't given "At the moment, who knows? Anyway, I'm a well-known actor and a musician and a first-rate mathematician. I can't remember any equations thought of it, and it didn't seem right. She sighed and drew away. "That was a lucky guess on your age." Did that mean he wasn't right on anything else? From the expression beginning. Can't you really tell who I am?" "I can't "That should be the top of Dan Merrol's head," she said softly. thought it comforted. "I waited till I was sure. I didn't want to upset you." He wasn't as sure as she seemed to be now. Somehow, maybe he was still Dan Merrol—but he wasn't going to insist on it—not after looking at himself. Not after trying to sort out those damned memories. she hadn't. At that time, she must have half-believed he was Dan Merrol, still dangerously near the edges of post-regrowth shock. She was looking at him, waiting for that explanation. He shook his mind frantically and the words came out. "Self-therapy," he said patient carefully." Merrol." At least he knew who or what Dan Merrol was—the pilot of the Mars Erica he didn't remember at all, save from last night, and what was that due to? "What are you going to do?" he asked, deliberately toying with the last bite of breakfast. It gave him time to think. "They said they'd identified everyone, living or dead, and I supposed they had. After seeing you, I can believe they made any number of similar mistakes. Dan Merrol may be alive under another name. It will fell." Even if he was sure, he didn't know whether he could tell her—and he The receptionist was busy with the drawer of the desk. "Can I help you?" she asked, continuing to peer down. "The director—Doctor Crander. I don't have an appointment." "Then the director can't see you." The girl looked up and her firmly polite expression became a grimace of barely suppressed laughter. reserved for Erica. "Glad to see you," said Doctor Crander, behind the desk. He was nervous and harassed for so early in the morning. "The receptionist didn't give me your name. For some reason she seems upset." hospital didn't seem to have a calming influence on either her or the doctor. "That's why I came here. I'm not sure who I am. I thought I was Dan Merrol." Doctor Crander tried to fight his way through the desk. Being a little wider and solider, though not by much, the desk won. He contented himself by wiping his forehead. "Our missing patient," he said, sighing "Then I am Dan Merrol?" The doctor came cautiously around the desk this time. "Of course. I Crander frowned, his nervousness rapidly disappearing. "Then it was about an hour ago. We didn't think you could walk at all so soon, or we would have kept someone on duty through the night." The doctor took his pulse. "Seems fine," he said, surprised. "Sit down—please sit down." Without waiting for him to comply, Crander pushed him into a chair and began hauling out a variety of instruments with which he poked about his bewildered patient. Finally Crander seemed satisfied. "Excellent," he said. "If I didn't know better, I'd say you were almost fully recovered. A week ago, we considered removing you from the regrowth tank. Our decision to leave Merrol wasn't as pleased as the doctor appeared to be. "Granted you can identify me as the person who came out of regrowth—but does that mean I'm Dan Merrol? Could there be a mistake?" Crander eyed him clinically. "We don't ordinarily do this—but it is evident that with you peace of mind is more important than procedure. And you look well enough to stand the physical strain." answered. "Miss Jerrems, the Dan Merrol file." They see me and flee as fast as they can caper , thought Merrol. It was not wholly true—Crander didn't seem much affected. But he was a doctor and used to it. Furthermore, he probably had room for only one emotion at the moment—relief at the return of his patient. mass of records. Crander noticed his expression and smiled. "You're our prize case, Merrol. I've never heard of anyone else surviving such extensive surgery. Naturally, we have a step-by-step account of the adoration she had showed so openly for her employer seemed to have curdled in the last few moments. Crander dug into the files and rooted out photographs. "Here are pictures of the wreckage in which you were found—notice that you were Merrol winced. The photographic sequence was incontrovertible. He had why—no one knows. But it is true that cells differ from one body to the next, and this test detects the difference." The mass-cell radiographs did seem identical and Dr. Crander seemed certain. Taken altogether, the evidence was overwhelming. There had been no mistake—he was Dan Merrol, though it was not difficult to "You did a fine job," he said. Recalling the picture of the wreckage, he knew they had. "But couldn't you have done just a little better?" Crander's eyebrows bounced up. "We're amazed at how well we have done. You can search case histories and find nothing comparable." His eyebrows dropped back into place. "Of course, if you have a specific "Perhaps—taken by itself." Dan rolled up his sleeve. "See how it joins the forearm." Crander waggled it gravely. "It coordinates perfectly. I've observed you have complete control over it. The doctor's eye, my boy. The doctor's diagnostic eye." ?" cried the doctor. "Do you have any idea of the of surgical skill." He moved the hand experimentally, to show Merrol how it was done. He dropped the hand and hurried to a screen against the wall. Crander drew his finger across the surface and the mark remained. "You know about Rh positive and negative blood. Mixed, they can be lethal. This was discovered long ago, by someone I've forgotten. But there are Dr. Crander seemed about to pluck one of Dan's eyes from its socket. fact there wasn't any time at all—we actually thought you were dead, but soon found we were wrong." Crander stared at a crack in the ceiling. "Further recovery will take other operations and your nervous system isn't up to it." He shook his head. "Five years from now, we can help you, not before." Merrol turned away miserably. There were other things, but he had brain." "Brain?" Dan was startled. "How hard do you think your skull is?" Crander came closer. "Bend your head." Merrol obeyed and could feel the doctor's forefinger slice across his from shock. In addition, other sectors were damaged and had to be replaced." Crander traced out five areas he could feel, but not see. "Samuel Kaufman, musician—Breed Mannly, cowboy actor—George Elkins, lepidopterist—Duke DeCaesares, wrestler—and Ben Eisenberg, It was no wonder Erica had cringed at their names.

<question>:
How is doctor Crander sure that this patient is Dan Merrol?

<options>:
A Mass-cell radiographs match pre- and post-surgery
B Blood work proves matching DNA
C The physical appearance most aligns with the pre-surgery Merrol
D Crander is not sure

<answer>:

A