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

<passage>:
sag of the dust I learned to spot a passable crack, and tell it had no stomach for mysteries, vast or trifling, and there were pressing things to think about at this time. Yet the doorman at first. Too smoothly, it seemed to me, and the others seemed to think so, too. McIvers’ restlessness was beginning to grate on our nerves. He talked too much, while we were resting or while we were wisecracks, witticisms, unfunny jokes that wore thin I figured that it would pass off after a while. I was apprehensive I just managed to hide it better. he looked weary and immensely ugly. His cheeks and penultimate blow to our already fraying nerves. He had driven down a side-branch of a long canyon running off west of our route and was almost out of sight in a cloud of ash when we heard a sharp cry through our earphones. I wheeled my Bug around with my heart in my throat and and, for once, he didn’t have anything to say. It was the wreck of a Bug an old-fashioned half-track model of the sort that hadn’t been in use for years. It was wedged tight in a cut in the rock, an axle broken, its casing split wide open up the It looked the same, but every now and then it details Why? What was wrong with your glass? Your filters? We’ve I picked my way more cautiously then. We were getting into an area of recent surface activity “You want to know why we failed?” asked Claney. I caught myself wishing that the Major had okayed more dangerous for to know.” “It’s simple. We failed because it can’t be done. We couldn’t do it and neither can you. No human beings will ever cross much about the others. I was worried about One error in judgment could sink us all, but I wasn’t thinking the Brightside alive, not if they try for centuries.” can blame the equipment or the men—there were flaws in It wasn’t healthy thinking and I knew it, but I couldn’t get the It was the thought out of my mind. that whipped us, that and the broad flat plateau, dodging a network of gaping surface cracks—winding back and forth in an effort to keep the machines on solid rock. I couldn’t see far ahead, because of the yellow haze the Bug again, we moved still more slowly—edging out on a then I edged my Bug I think. I followed the news stories like a tri-V serial and then I was heartbroken when they just disappeared. I know now that they were a pair of idiots, starting off without proper equipment, with practically no knowledge of surface conditions, without any charts—they couldn’t have made a hundred miles—but I didn’t know that then and it was a a section of the fault like a ramp. Even as I watched it, I could feel the surface crust under the Bug trembling and saw the since the Matto Grasso. Then he made the attempt on Vulcan the sort of guy who always had things figured a little further place. Too many men in this game are all nerve and luck, and how he preferred a hot trek to a cold one any day of the “No particular plans,” I told him. “Why?” “What trip?” I’d thought of it a thousand times and never dared consider That makes the Brightside of Mercury at perihelion the hottest It would be a hellish trek. Only a few men had ever learned how installation with a human crew could survive at either temperatures. The Major was counting on Sanderson knowing something liable to get awfully uneasy and none of them can We had four Bugs, three of them the light pillow-tire models, with special lead-cooled cut-in engines when the heat set in, isn’t he?” “Maybe. He’s lucky and skillful. Where do you draw the The Major laughed. “I don’t think we need to worry about they were. The best available were pretty poor, taken from so far out that the detail dissolved into blurs on blow-up. They showed the biggest ranges of peaks and craters and faults, and that was all. Still, we could use them to plan a broad outline of our course. tracings suggest a lot of activity in that region, getting worse down toward the equator—not only volcanic, but sub-surface Stone nodded. “Sanderson told me there was probably constant surface activity.” The Major shrugged. “Well, it’s treacherous, there’s no doubt of it. But the only way to avoid it is to travel over the Pole, which would lose us days and offer us no guarantee of It seemed that the more we considered the problem, the further we got from a solution. We knew there were active localized. But there were problems of atmosphere on Brightside, as well. There was an atmosphere and a constant atmospheric 2 , and nitrogen, and traces of that avoided those upheavals as far as possible. But in the final he couldn’t see why everyone should get so excited. Evidently the Major decided not to press the issue of his like this, and some of the best wouldn’t seem to be the most reliable at first glance. Anyway, personality problems weren’t our big problem right then. worried us first and one had an inner lining of a fiberglass modification, to avoid the clumsiness of asbestos, and carried the refrigerating unit the two layers. Warning thermocouples, of course—at “How about the Bugs?” “They were insulated, too, but we weren’t counting on them too much for protection.” approach to the Sun—which made Center the hottest part of the planet at the hottest it ever gets. The Sun was already huge and yellow over the horizon the surface was really treacherous. what terrain we had to cross. Detours would be dangerous and time-consuming. Delays could cost us our lives. We all knew that. the individual, maybe, but I was driving blind now and I didn’t He stared at the Major. “I mean, how can we tell what sort of sharply. “Charts! I’m talking about detail work. We don’t need to worry about the major topography. It’s the little faults you can’t see on the pictures that can kill us.” He tossed the charts down excitedly. “Look, let me take a Bug out ahead and work “No dice,” the Major broke in. “But why not? We could save ourselves days!” break, hotter and hotter with every mile. We knew that the first few days would be the easiest and we were rested and I moved out first Even at only 30 per cent Earth gravity they were a strain on I kept my eyes pasted to the big polaroid binocs, picking out the heat so much those first days out. We The Major measured water out with an iron hand, because we’d have drunk ourselves into nephritis in a week otherwise. reasons—but all we knew, or cared about, was that it happened to be so. We didn’t sleep the first few stops, as a consequence. Our eyes burned in spite of the filters and we had roaring headaches, the wheel. We were moving down into desolation that made the challenge was so powerful you could almost feel it. No one tried it had been cruelly punished, but the land was still there, so it had to be crossed. Not the easy way. It had to be crossed the hardest way possible: overland, through anything the land could throw up to us, at the most difficult time possible. Yet we knew that even the land might have been conquered and won. We’d never fought heat like this and won. The only worse heat in the Solar System was the surface of the Sun itself. onto the slope of a range of ragged craters that ran south and east. This range had shown no activity since the first landing face of the planet. Not enough for erosion, though. The craters rose up out of jagged gorges, huge towering spears of rock and rubble. Below were the vast yellow flatlands, smoking and hissing from the gases beneath the crust. Over everything was gray dust—silicates and salts, pumice and limestone and granite ash, filling crevices and declivities—offering a soft, treacherous surface for the Bug’s pillow tires. I learned to read the ground, to tell a covered fault by the

<question>:
What likely caused the most problems?

<options>:
A the toxic gases
B the high temperatures
C vehicle trouble
D incorrect mapping

<answer>:

B