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

<passage>:
Warrior of Two Worlds By MANLY WADE WELLMAN He was the man of two planets, drawn through the blackness of space to save a nation from ruthless invaders. He was Yandro, the Stranger of the Prophecy—and he found that And at once there was an answer: " You lie upon the world Dondromogon. " I knew the language of that answer, but where it came from—above, beneath, or indeed within me—I could not say. I lifted a hand, and knuckled dust from my eyes. "How did I get here?" I demanded of the speaker. "It was ordered—by the Masters of the Worlds—that you should be brought from your own home planet, called Earth in the System of the star called Sun. Do you remember Earth?" The voice had a note of triumph. "You do not know that. It is as well, for this will be a birth and beginning of your destined leadership on Dondromogon." "Destined—leadership—" I began to repeat, and fell silent. I had worlds away, for a specified purpose here on whatever windswept planet Dondromogon might be. "Birth and beginning—destined leadership—" Fantastic! And yet, for all I could say to the contrary, unvarnishedly true. "It is a world the size of your native one," came words of information. "Around a star it spins, light-years away from the world of your birth. One face of Dondromogon ever looks to the light and heat, wherefore its metals run in glowing seas. The other face is ever away unceasing, bitter, with no quarter asked, given or expected. Masters ." The voice became grand. "Suffice it that you were and drawn roughly erect. The touch restored my senses, and I wrenched a curved stock to fit the palm of the hand, borne snugly in a holster. its scabbard. "If he's dead, we get pay for both warning and capture—" His thumb touched a button at the pommel of the hilt. The dull blade He whimpered and swore, and his glowing sword dropped. Its radiant that seemed to spring on me like a long thin snake and to fasten coil "What's this?" Beyond, it gave into several passages. She chose one of them and "I tell the truth," was my reply, not very gracious. "You will have to prove that," he admonished me. "What proof have I?" I demanded. "On this world of yours—Dondromogon, isn't it called?—I'm no more than an hour old. Accident or shock has taken my memory. Let me have a medical examination. A scientist You mystic doctors are too apt to become fuddled—" "But it is, it is!" The graybeard flourished a thin hand at me. "Look at him, you of little faith! Your mind dwells so much on material strength that you lose touch with the spiritual—" study," he commanded. "On the shelf behind my desk, bring the great gold-bound book that is third from the right." Then he turned back, and bowed toward me. "Surely you are Yandro, the Conquering Stranger," he said, intoning as if in formal prayer. "Pardon these short-sighted ones—deign to save us from our enemies—" Old Sporr almost crowed. "You see? If he was a true imposter, he would come equipped with all plausible knowledge. As it is—" "As it is, he may remember that the Conquering Stranger is foretold old and well-thumbed, with dim gold traceries on its binding. Sporr "I still say you will understand my caution," he addressed me, with real respect and shyness this time. "If you are Yandro himself, you can prove it. The prophecy even sketches a thumb-print—" And he held the book toward me. It contained a full-page likeness, in color, of myself wrapped in a one side a thumb-print, or a drawing of one, in black. men take into thought. The ears in the picture are like the ears of the artfully done by the Newcomers, and the red mantle he wears more easily assumed." thumb-print—" "Oh, yes, the thumb-print," I repeated wearily. "By all means, study my thumbs, if you'll first take these bonds off of me." bustled to me. From under his robe he produced a pouch, and took out a pencil-sized rod. Gingerly opening the red mantle, he touched my tether in several places with the glowing end of the rod. The coils dropped "Thumb-prints?" I offered. carefully anointed one of my thumbs, and pressed it to the page. All Rohbar, field commander of this defense position," he said with crisp respect. "Sporr is a mystic doctor, full of godly wisdom. Doriza, a junior officer and chief of the guard. And you—how could you know?—are sent by the First Comers to save us from our enemies." level of light and sound. "Our cities are below ground," he quavered. "Whipped by winds above, we must scrabble in the depths for life's necessities—chemicals to transmute into food, to weave into clothing, to weld into tools and "I have arranged for that," Sporr began, then fell silent, fingers jelly, a little bundle of transparent leaves or scraps like cellophane mid-thigh. A resilient band at the top, with a series of belt-holes, garment, a long strip of soft, close-woven fabric that spiralled below the knee, like buskins. The case also held a platinum chain for the neck, a belt-bag, and a handsome sword, with clips to fasten them and dark and moody—small wonder!—the chin heavy, the mouth made grim beard. Then he bowed, supple and humble, his palms together. crossed the room. A sort of mouthpiece sprouted from the wall. "I announce," he intoned into it. "I announce, I, Sporr, the reader and that I was fated to live when he returned for the rescue of all Dondromogon." mixture of awe and brightness. "It is necessary that we live like this," she explained. "The hot air of Dondromogon's sunlit face is ever rising, and the cold air from the dark side comes rushing under to fill the vacuum. Naturally, our together? They should fight, not each other, but the elements." Doriza had no answer that time, but Sporr spoke up behind us: "Great Yandro is wise as well as powerful. But the Newcomers do not want to help, not even to conquer. They want to obliterate us. There is nothing sheet of dull metal. She spoke into a mouthpiece: inspiring were it not so blatantly dyed. The other was a little wisp of Silence then, a silence which evidently I must break. I broke it: infant. I hear wonderful things, of which I seem to be the center. Are they true?" "The tenth part of the wonders which concern mighty Yandro have not been told," intoned Sporr, ducking his bearded head in a bow, but the dignified folds of his purple robe. One carefully-tended hand "Barak was a brute—mighty, but a brute." Thus Gederr continued. "Weapons in his hands were the instruments of fate. His hands alone caused fear and ruin. But it pleased our fortune-bringing stars to encompass his destruction." He grinned, and licked his full lips. "Now, even as they are without their battle-leader, so we have ours." "You honor me," I told him. "Yet I still know little. It seems that I am expected to aid and lead and save the people of this world called Dondromogon. But I must know them before I can help."

<question>:
What is the significance of the narrator’s thumb print?

<options>:
A It is proof that he is Yandro
B It is proof that he is from Earth
C It is proof that he is a Newcomer
D It is proof that he is a Master of Worlds

<answer>:

A