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

<passage>:
writer, was in a jam again. What with red-spot fever, talking cockatoos and flagpole trees, I was running in circles—especially since Grannie became twins every now and then. Five minutes after my ship had blasted down, the four of us met in the offices of Interstellar Voice I scowled at that it didn't make sense. not up on the scientific reasons, but it seems that life on the red apparatus, and the rush was on." "What do you mean?" crossed the Baldric without trouble." "What sort of trouble?" Grannie Annie had demanded. And when Antlers Park stuttered evasively, the old lady snorted, "Fiddlesticks, I never saw trouble yet that couldn't be explained. We leave in an hour." Steadily the four travelers approached. Then, when a dozen yards away, they suddenly faded like a negative exposed to light and disappeared. "What do you make of it?" I said in a hushed voice. Grannie shook her head. "Might be a form of mass hypnosis superinduced by some chemical radiations," she replied. "Whatever it is, we'd better repetition of the "mirage." The wind continued to blow ceaselessly, and the sand seemed to grow more and more powdery. Grannie's eyes glittered. "Trouble with the mine laborers?" she questioned. excellent living conditions with a vacation on Callisto every year. Up until a short time ago most of them were in excellent health and spirits. Then the Red Spot Fever got them." "Red Spot Fever?" Grannie looked at him curiously. Jimmy Baker nodded. "The first symptoms are a tendency to garrulousness on the part of the patient. Then they disappear." He paused to make an adjustment of the windlass. "They walk out into the Baldric," he continued, "and nothing can stop them. We tried following them, of course, but it was no go. As soon as they realize they're being followed, they stop. But the moment our eyes "There must be ways of stopping this," she said. "Have you called in any physicians? Why don't you call an enforced vacation and send the men away until the plague has died down?" Baker shook his head. "Three doctors from Callisto were here last month. They were as much at loss as I am. As for sending the men away, I may have to do that, but when I do, it means quits. Our company is chartered with Spacolonial, and you know what that means. Failure threw off the switch. "The entire crew of Shaft Four have gone out into the Baldric," he said slowly. There was a large map hanging on the wall back of Baker's desk. Grannie Annie walked across to it and began to study its markings. level where a huge laboratory and experimental shop ran the length of the building. Grannie seized a light weight carry-case and began roll down the ramp. Not until they had vanished in the desert haze did I sense the loneliness of this outpost. With that loneliness came a sudden sense of foreboding. Had I been a fool to let Grannie go? I thought of her, an "Let's look around," I said. We passed down the corridor and climbed the staircase to the second floor. Here were the general offices of were Jimmy Baker, Grannie, and Xartal. It was as if I were standing directly behind them. entered the room. It stopped abruptly. "The machine uses a lot of power," the operator said, "and as yet we haven't got much." The cloud of anxiety which had wrapped itself about me disappeared somewhat as I viewed this device. At least I could now keep myself posted of Grannie's movements. Karn and I went down to the commissary where we ate our supper. When we returned to Jimmy Baker's office, the visiphone bell was ringing. Miss Flowers there?" "Miss Flowers left with Mr. Baker for Shaft Four," I said. "There's trouble up there. Red spot fever." "Fever, eh?" repeated Park. "That's a shame. Is there anything I can do?" "Tell me," I said, "has your company had any trouble with this plague?" "A little. But up until yesterday the fever's been confined to the other side of the Baldric. We had one partial case, but my chemists gave the chap an antitoxin that seems to have worked. Come to think of I haven't been out in the Baldric for years, but if you didn't have any trouble, I shouldn't either." We exchanged a few more pleasantries, and then he rang off. In exactly an hour I went upstairs to the visiscreen room. Then once more I was directly behind my friends, listening in on their conversation. The view through the windscreen showed an irregular array "There's an eyrie over there," Jimmy Baker was saying. "We might as well camp beside it." Moments later a rude circle of flagpole trees loomed ahead. Across the top of them was stretched a translucent web. Jimmy and Grannie got out of the car and began making camp. Xartal remained in his seat. He was group of Earth people suddenly materialized on the eyrie, talking and moving about as if it were the most natural thing in the world. "Sorry," the operator said. "I've used too much power already. Have to give the generators a chance to build it up again." Nodding, I turned and motioned to Karn. We went back downstairs. "That explains something at any rate," the old prospector said. "But how about that Red spot fever?" On Jimmy Baker's desk was a large file marked: FEVER VICTIMS. I opened it and found it contained the case histories of those men who had been attacked by the strange malady. Reading them over, I was struck by one detail. Each patient had received the first symptoms, not while working in the mines, but while sleeping or lounging in the barracks. Five minutes later Karn and I were striding down a white ramp that led to the nearest barracks. The building came into sight, a low rectangular structure, dome-roofed to withstand the violent winds. Inside double tiers of bunks stretched along either wall. In those bunks some thirty men lay sleeping. The far wall was taken up by a huge window of denvo-quartz. As I stood there, something suddenly caught Ezra Karn's eye. He began to walk part of the button appeared to be a powerful lens of some kind, and as I seized it and pulled it loose, I felt the hum of tiny clock work. All at once I had it! Red spot fever. Heat fever from the infra-red rays of Jupiter's great spot. Someone had constructed this lens to concentrate and amplify the power of those rays. The internal clockwork served a double purpose. It opened a shutter, and it rotated the lens slowly so that it played for a time on each of the sleeping men. I slid the metal button in my pocket and left the barracks at a run. Back in the visiscreen room, I snapped to the operator: "Turn it on!" I headed for that entrance, and when I reached it, I shut off power with an exclamation of astonishment. contrivance that looked not unlike a search lamp. A blinding shaft of vibratory scale and the only thing that will combat the infra-red rays that cause red spot fever. Those men won't stop walking until they've reached Shaft Four." Grannie Annie told her story during the long ride back to Shaft Four. this Eighth Moon, so also was that spot a deadly power in itself, capable when its rays were concentrated of causing a fatal sickness. Then suddenly becoming fearful of Grannie's prying, Antlers Park strove to head her off before she reached Shaft Four. He did head her off and managed to lure her and Baker and Xartal into the Shaft barracks where they would be exposed to the rays from the lens button. But Grannie only pretended to contract the plague. Park then attempted to outwit Ezra Karn and me by returning in Jimmy

<question>:
What was a common factor with all the victims of the Red Spot Fever?

<options>:
A They were all treated in the Baldric
B They had all started investigating the odd birds and their strange behavior
C They had all started seeing symptoms in the mines
D They had all started seeing symptoms in the barracks

<answer>:

D