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

<passage>:
had stumbled onto a murderous plot more hair-raising than any she had ever concocted. And the danger from the villain of the piece didn't worry her—I was the guy he was shooting at. I was killing an hour in the billiard room of the Spacemen's Club Spacemen's was a sanctuary, a rest club where in-coming pilots and crewmen could relax before leaving for another voyage. The rule that no females could pass its portals was strictly enforced. fish-face to shut up." "Okay, okay," I grinned. "Look, we'll go into the grille. There's no allowed in the Spacemen's "It wasn't Guns Pistols and it wasn't Ganymede ." I grinned. "All complete, I'll bet, with threats against the universe zilcon wood seats and dingy atobide lamps. But the place was packed with miners, freight-crew-men—all the tide and wash of humanity somewhere and talk." She minced lightly down the aisle, climbed the stage steps and disappeared in the wings. "That damned fossilized dynamo," I muttered. "She'll be the death of me yet." Earthman operator. A tall man, clad in a claw-hammer coat, came out from the wings and There was a roar of applause from the the visi sets. Isolated miners on Jupiter, dancers in swank Plutonian The audience in the Satellite seemed to have lost much of its general surveying his army. His black eyes gleamed, and his thin lips crowd. It was outside under the street marquee that a strange incident the Red Planet. But the thing that happened there was a throw back to an earlier era. Someone shouted, "Yah, yellow-face! Down with all Kagors!" As one man the crowd took up the cry and surged forward. The helpless Kagor into his mouth. Moments later an official hydrocar roared up and a dozen I.P. men rushed out and scattered the crowd. But a few stragglers lingered to THE JET. Inside was a deep room with booths along one wall. The place was all but deserted. I nodded. "As disgraceful an exhibition as I've ever seen. The I.P. men ought to clamp down." "The I.P. men aren't strong enough." projected at high speed. But the character of the Gamma rays has never been completely analyzed. Like those set up by radium, they are I was sitting up now, hanging on to the woman's every word. "Now in 2710, as you'd know if you studied your history, the three planets of Earth, Venus, and Mars were under governmental bondage. The cruel dictatorship of Vennox I was short-lived, but it lasted long enough to endanger all civilized life. "The archives tell us that one of the first acts of the overthrowing ordered must be kept in each household. The effect on the people was representation be abolished on Jupiter. The time is ripe for a military dictator to step in. approaching danger. "Let's get out of here," I said, getting up. A heat ray! Grannie Annie leaped to her feet, grasped my arm and raced for the door. Outside a driverless hydrocar stood with idling motors. The old woman threw herself into the control seat, yanked me in after her and threw over the starting stud. An instant later we were plunging through the dark night. , the tough little two headed pack animal of the Venus hinterland. Any form of plane or rocket would have had its motor instantly destroyed, of course, by the magnetic force belt that encircled the planet's equator. Now our drivers changed to boatmen, and we loaded our supplies into three clumsy jagua canoes. the lost space ship. Our job is to find that ore and destroy it. You see, I'm positive the Green Flames have never been removed from the ship." Sleep had never bothered me, yet that night I lay awake for hours that broadcast would have meant little, a slight rebellion here, an place a ringing silence blanketed everything. From the tent opposite a gaunt figure clad in a familiar dress "Stand still!" The thing in the darkness turned like a cam on a rod and drove at us again. This time the old woman's heat gun clicked, and a tracery of ground and shot aloft. Grannie Annie fired with deliberate speed. trained to pursue a quarry until it kills. It has a single unit brain and follows with a relentless purpose." "Then that would mean...?" "That it was sent by our enemy, the same enemy that shot at us in the tent and faced me with earnest eyes. "Billy-boy, our every move is being watched. From now on it's the survival of the fittest." the swamp had undergone a chemical change and evolved into a cohesive multi-celled marine life that lived and died within a space of hours. The Venusians paddled with extreme care. Had one of them dipped his hand into one of those yellow streaks, he would have been devoured in a matter of seconds. At high noon by my Earth watch I sighted a low white structure on one of the distant islands. Moments later we made a landing at a rude "What do you mean?" Grannie paused in the act of rolling herself a cigarette. "You know where it is, don't you?" "Ye-s," Karn nodded. "But like I told you before, that ship lies in Earthmen. Strictly speaking, they're no more than a form of energy." "Dangerous?" "Yes and no. Only man I ever heard of who escaped their country outside of myself was the explorer, Darthier, three years ago. I got away because I was alone, and they didn't notice me, and Darthier escaped Food supplies and fresh drinking water were replenished at the hut. my thoughts far away. Half an hour later we headed into the unknown. The Venusian boatmen were ill-at-ease now and jabbered among themselves constantly. We camped that night on a miserable little island where insects swarmed despondency beset our entire party. I caught myself musing over the futility of the venture. Only the pleadings of Grannie Annie kept me from turning back. On the morrow I realized the truth in her warning, that all of us had been exposed to the insidious radiations. steaming swamp.... But at length we reached firm ground and began our advance on foot. It was Karn who first sighted the ship. Striding in the lead, he suddenly halted at the top of a hill and leveled his arm before him. There it lay, a huge cigar-shaped vessel of blackened A rectangular metal envelope had been constructed over the stern quarters of the ship. Above this structure were three tall masts. And suspended between them was a network of copper wire studded with white insulators. Venusians and head across the knoll," she ordered. "Ezra and I will circle in from the west. Fire a gun if you strike trouble." But we found no trouble. The scene before us lay steeped in silence. Moments later our two parties converged at the base of the great ship. A metal ladder extended from the envelope down the side of the vessel. Mid-way we could see a circular hatch-like door. The silence remained absolute. We reached the door and pulled it open. There was no sign of life. left side by a wall of impenetrable stepto glass. The corridor was bare of furnishings. But beyond the glass, revealed to us in mocking Karn raised the butt of his pistol and brought it crashing against the "You'll never do it that way," Grannie said. "Nothing short of an atomic blast will shatter that wall. It explains why there are no guards here. The mechanism is entirely self-operating. Let's see if the Green Flames are more accessible." the feeble shafts of daylight that filtered through cracks in the Suspended by insulators from the ceiling over them was a thick metal

<question>:
Why were there no guards present in the ship?

<options>:
A They had all been eliminated by the Green Flames
B the metal envelope was the only guard
C The ship was well hidden to not need guards
D The ship was self-operating to defend

<answer>:

D