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

<passage>:
The Last Monster By GARDNER F. FOX Irgi was the last of his monster race, guardian of a dead planet, master of the secret of immortality. It was he whom the four men from Earth had to conquer to gain that secret—a tentacled Extensive research did not uncover any evidence that the U.S. copyright on this publication was renewed.] Irgi was the last of his race. There was no one else, now there had been no others for hundreds and hundreds of years. Irgi had lost count but he knew that much. There were no others. Only Irgi, alone. clinging shelter, destroying dust and germs. Irgi had discovered the mist many years ago, when it was too late to save his kind. Urg and set them up. Irgi enjoyed beauty, and he enjoyed work. It was the combination of both that kept him sane. In the doorway, Irgi paused and ran his eyes about the chamber, sighing. block possess. There was nothing they could not do, if Irgi so willed. It was another discovery that came too late to save the Urg. Irgi moved across the room. He pressed glittering jewels inset in a Irgi drew himself upwards, slowly turning, laving in the quivering Irgi was immortal, and the blue light made him so. "I must speak," Irgi said as he moved along the corridor. "I have not will talk to them and tell them how lonely Irgi is." and the name and fame of Irgi means nothing to the walls of my city, nor to the Chamber of the Cones, nor even—at times—to Irgi himself." "The last planet in our course," he breathed. "Maybe it has the radium!" "Yes," whispered the man beside him, wetting his lips with his tongue. "No use to think of failure. If it hasn't, we'll die ourselves, down there." Radium. And the Plague. It had come on Earth suddenly, had the Plague, back in the first days of space travel, after Quigg, the American research scientist at Cal Tech, discovered a way to lift a rocket ship all like the sleek craft that plied the voids today. But it had been a beginning. And no one had thought anything of it when Quigg, who had made the first flight through space, died of cancer. As the years passed to a decade, and the ships of Earth rode to Mars and Venus, it began to be apparent that a lifetime of space travel meant a hideous death. Scientists attributed it to the cosmic rays, for out in space there was no blanketing layer of atmosphere to protect the fleshy tissues of man from their piercing power. It had long been cosmos perhaps they were, said some, the direct cause of life. Thus by causing the unorderly growth of new cells that man called cancer, the cosmic rays were destroying the life they had created. It meant death to travel in space, and only the stupendous fees paid to the young men who believed in a short life and a merry one, kept the and an inner coating of lead brought men into port raving with lead poisoning illusions. Cancer cases increased on Earth. It was learned that the virulent form of space cancer, as it was called, was in some peculiar manner, contagious to a certain extent. The alarm spread. Men who voyaged in space were segregated, but the damage had been done. The Plague spread, and ravaged the peoples of three planets. Hospitals were set up, and precious radium used for the fight. But the radium was hard to come by. There was just not enough for the job. barge by comparison. And mankind gave it to Valentine Emerson to take it out among the stars to find the precious radium in sufficient quantities to halt the Plague. It had not been easy to find a crew. The three worlds knew the men were going to their doom. It would be a miracle if ever they reached a single planet, if they did not perish of space cancer before their first goal. Carson Nichols, whose wife and children were dying of the Plague, begged him for a chance. A murderer convicted to the Martian salt mines, Karl Mussdorf, grudgingly agreed to go along on the promise we die." He ran quivering fingers over his forearm, felt the strange lumps that heralded cancer. Involuntarily, he shuddered. "There it is, Karl," said Nichols. "Start hoping." Mussdorf scowled darkly, and spat. "A hell of a way to spend my last days," he growled. "I'm dying on my feet, and I've got to be a martyr to a billion people who don't know I'm alive." "You know a better way to die, of course," replied Emerson. dying a pleasure. In fact," he chuckled softly, "that's just the way I'd let her kill me." stood staring out, gasping. "Wot's happenin' now?" choked Gunn. No disease." He began to laugh, then caught himself. "No disease," he whispered, "and every one of us is going to die of cancer." Mussdorf came up through the trap and passed out the sun-blasters. They buckled them around their waists while Mussdorf swung the bolts of the Irgi stared at the things that lay on the white flagging. Queer beings they were, unlike anything Irgi had ever conceived. Only two legs, only short work of them if an Urgian cat existed any more, and Irgi had Irgi bent to wrap long arms about the queer beings, lifting them. His eyes were caught suddenly by the lumps protruding from their arms and legs, from face and chest. The growth disease! That was bad, but Irgi knew a way to cure it. Irgi knew a way to cure anything. electrigraph screen. That should be absorbing. It made Irgi happy, reflecting upon it, and Irgi had not known happiness for a long time. Irgi dropped his burdens. With quick tendrils he adjusted straps to electric charges all intelligent beings cast," Irgi said aloud, glad at "I wonder if they've perfected this," Irgi mused. "They must be aware grew nebulous, then cleared. Irgi disease. Now he beheld the mighty salt mines where naked men swung huge picks at the crusted crystals, sweating and dying under a strange sun. Even these remnants of humanity festered with the growth. A tall, lean man in white looked out at him. His lips moved, and Irgi plague. The thoughts of this Emerson were coming in clearer, as Irgi in Irgi stared upward at a colossal figure graven in lucent white marble. Why, he had the power to make himself immortal! These creatures would but he could save it ! Irgi unfastened clamps, and rolled the screen aside. He reached to a "When they realize that I am their friend, they will gladly hear my counsels!" Opening the laboratory door, Irgi passed out and closed it behind him. He flipped his head to right, to left saw the others stretched out and strapped even as he. They were unconscious. What right had they to then bit down again, hard. Nichols screamed suddenly, his body aching. It woke the others. They too, bellowed and screamed and sobbed, and their arms and legs writhed like wild things in a trap. He dropped back, sobbing. "That fiend," yelled Mussdorf. "That ten-eyed, octopus-legged, black-hearted spawn of a mismated monster did this to us. Damn him! Damn him! If I ever get loose I'll cut his heart out and make him eat it." "Maybe—maybe he's vivisecting us," moaned Nichols. "With rays or—or mine convict. I'd have done anything to get out of that boiling hell. I volunteered to go with you for the radium. Me and Gunn. Nichols doesn't count. He came on account of his wife and kids. We were the only two who'd come. Convicts, both of us."

<question>:
What is the most likely reason Irgi was the last of his people?

<options>:
A They were killed in an invasion
B They died from a disease caused by a microbe
C They moved to another planet
D They died from cancer

<answer>:

D