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

<passage>:
interstellar space to devour Earth. They gnawed this gutted cosmic carcass, could humanity flee? Westover got a shock when he stumbled onto the monster, for all that he flood, and behind him, too, the rising water he had barely escaped. The He recoiled as if seared, and retreated, slithering in the muck. For over the hills on either side, five miles apart. The beast was And that explained the flood the monster's body had formed an Westover stood motionless in the blackness moon through a rift of the cloud blanket brought him awake ahead was blocked by the titanic enemy. Then the impersonal will that had driven him implacably two days and nights without stopping came to his rescue. Westover plodded forward, the monster's foot, and sought above him with upstretched hands—found minutes after he had found a new foothold merely clung panting with himself, gasping and quivering, to comparative safety on the broad steep that rose to the summit of the monster's humped back, a mountain to be climbed. Westover felt poignantly that his exhausted body could which he had to make before dawn ... but not now ... not now.... He lay in a state between waking and dreaming, high on the monster's Westover had been one of the men who, in the days when humanity was Westover no longer saw the murky moonlight, the far faint glitter of from a circling jet plane, an immense tree of smoke that rose and a single cell—like the slime molds, the Earthly life forms that most resemble them. the conquest of space. They accomplished it not by invention but by "The monsters who have descended on Earth must represent the end result of a long evolution completed in space itself. They are evidently deep-space beings, able to propel themselves from planet to planet and Westover awoke, feeling himself bathed by the cold sweat of sogged his clothes. That, and the sleep he had had, refreshed him and idea for stopping the monsters. Even as Westover began frantically climbing, out of that lightening monster would begin to move, to crawl eastward impelled by the same dim phototropic urge which must guide these things out of the interstellar around the Earth, gutting the continents and churning the sea bottoms, and by now whatever was left of human civilization must be starving For a man like Westover, who had been a scientist, it was not the human pride, the star-storming pride of mind and will—defeated by Near the crest of the monster's back, he stumbled and fell hands and that an attack of dizziness had made him fall, then he realized that He could stay where he was unharmed, of course. On the monster's back, of all places, he had nothing to fear from it or from others of its made him unable to descend. As he lay where he had fallen, he felt that had kept him doggedly plodding forward. the experiments necessary to prove his theory of how to destroy the laboratory on the monster's back. Of course the rolling motion would prediction had been a hundred percent correct. The monsters' hunger With a struggle Westover roused himself, first sitting up, then swaying to his feet, frowning with the effort to look sanely at the terrible inspiration that had come to him. The cloud blanket was breaking up, thing's surface round about. Westover laughed wildly with a sudden sense of power. He, the insignificant human mite, had made the Sutton make that the monsters, extraterrestrial though they were, were fire from the loose fibrous scale of the monster's back, and half an fought it sternly back and succeeded in keeping his strange meal down. the wound he had inflicted on the monster. on a dog. The monster crawled by day and rested by night was conducting an experiment.... His life on the monster's back was The sun was already up, and the monster should have begun once more its Westover's mind was beginning to function again cessation of the rock and sway had exorcised the lethargy that had lain upon him. He knew now that he had been almost insane for the time he monster's vitals, and in a flash of insight knew them for what they that had been killed by atomic bombs, the answer to the riddle of and that could be expelled to drive the monster in flight like a reaction engine. Rocket propulsion, of course, was nothing new to zoology it was developed ages before man, by the squids and by those The monster on which Westover had been living as a parasite was generating gases within itself, preparing to leave the ravished Earth. Hurriedly the man scrambled to the highest eminence of the back and and what he saw brought him to the brink of of the sea. While he slept the monster had crept beyond the coast hopelessly distant. Of course—the great beast would crawl into the sea, which would float its bloated bulk and enable it to accelerate and take flight. It would never have been able to lift itself into the air from the dry land. He should have foreseen that and made his escape in time. Now that he had solved the problem of human survival.... But the bright ocean of the days he had been on the monster's back, but the rape of Earth one-willed swarm that Earth's astronomers had at first taken for a Westover sat for a space with head in hands, hearing the faint "Help! Here I am! Help!" Then he sprang to his feet, gripping his hand-ax, and ran panting to and heal overnight "Who are you?" asked Westover, breathlessly but almost without surprise. Westover hesitated. "I'm not just imagining you?" he appealed. Westover was still not sure that the other was more than one of the Teacher next—risen to rob him of his last shreds of sanity. But he When, a few hundred yards nearer the monster's head, the other halted into utter blackness—Westover knew that both the Preacher and his own and Westover nodded this time with alacrity. and Westover climbed to his feet and stood, weak-kneed still, staring obtrude itself in his dazed mind—by fluorescent tubes, and filled with told Westover better than words that there was something hugely he and Westover froze in dumbfounded recognition. Bill. You're just in time—I think we're about to hoist anchor." His quick eyes studied Westover's face, and he gestured toward a packing "I stumbled onto it," Westover admitted. "I was wandering across country—my plane crashed on the way back from that South American . I think my pilot went nuts destruction from up there.... But I got out in one piece and started had a sure-fire way to do that—but I didn't realize then that it was too late to think of killing them off." Westover finished the brief account of his coming to dwell on the monster's back. The other grinned happily. "I haven't got so far with the theory," said Westover, "but I think from the beginning. But the monsters absorbed into themselves all the one way out—to transfer our parasitism to the only remaining food "The monsters almost defeated us, because of their two special always won the battle of adaptations before, because he could improvise new ones as the need arose. The greatest crisis humanity ever faced such a turmoil that putting it into effect was the devil's own job. making air now, which we're going to need when the monster's in space. "Then," Westover glanced appreciatively around, "it looks like the main —if he ever existed—has to be replaced by the manage to—infect—when they're clustered again in space." "Amen," agreed Sutton. But the gaze he fixed on Westover was oddly Westover flexed his hands involuntarily, like one who has been too the plan that had burned in him during his bitter wandering over Westover stared. "Why?" "No! Of course I realize—Well, I see what you mean—I think." Westover Westover bowed his head, but he had caught a curiously expectant glint

<question>:
What saved Westover when the monster was getting ready to take off?

<options>:
A A plane
B His own scientific ideas
C A man
D A ship

<answer>:

C