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

<passage>:
city of metal that glittered malignantly before the cautious advance of three awed space-scouters. edge of the city. Behind them the black pile rose, the dome of force a graceful movement of hand and arm he indicated the waiting city. a city—even a city like this one—in such surroundings. The men from the ship knew only the surface facts about this waiting geometric discovery. Theirs was the eleventh inter-planetary flight, and the previous ten, in the time allowed them for exploration while this planet was still close enough to their own to permit a safe return in their ships, had not spotted the city. But the eleventh expedition had, an hour ago, with just thirteen hours left during which a return flight could be safely started. So far as was known, this was the only city on the planet—the planet without any life at all, save tiny mosses, for a million years or more. And no matter which direction from Rodney's bony face was without expression. "Gives me the creeps, kind of. I wonder what they were like?" Wass murmured, "Let us hope they aren't immortal." metal band. "Defense," Rodney, several yards behind, suggested. The three crossed the metal band and walked abreast down a street, their broad soft soled boots making no sound on the dull metal. They passed doors and arches and windows and separate buildings. They moved them, people? Have you noticed how low everything is?" Rodney's laughter rose, too. Then, sobering—"Maybe they crawled." A nebulous image, product of childhood's vivid imagination, moved "If we don't hurry up and get through this place and back to the ship, we're very likely to find out." looked back along the straight, metal street they'd walked on, and past He straightened his shoulders. The city was alien, of course, and that There was a pause. Then Wass, defensively—"It's almost as if the city almost as if ... they were human up to a certain point, the point being, perhaps, some part of their minds.... Alien things, dark and subtle, things no man could ever comprehend. Parallel evolution on two inner planets of the same system? Somewhere, it's like a glass wall." "We're trapped, we're trapped, they are—" The glittering band was here, too, like a halo around a silhouette. this?" He shook his head angrily, saying, "Judging by reports of the rest of the planet, it must have been horribly radioactive at one time. All of it." "Man-made radiation, you mean." alien-made, anyhow. Perhaps they had a war." Wass' voice sounded startled. "Anti-radiation screen?" Rodney interrupted, "There hasn't been enough radiation around here for hundreds of thousands of years to activate such a screen." and stood watching him labor along the metal toward them. Wass stared down at the metal street, as if he could look through it. "I wonder where it gets its power?" He led the way through a shoulder-high arch in one of the tall buildings surrounding the square. The corridor inside was dim and corridor were of the same dull metal as the buildings' facades, and It was rather like ... entering a gigantic metal beehive. come to associate with the city builders. The three torches, shining "Another assumption," Wass said. "We have done nothing but make assumptions ever since we got here." think you're doing?" "We have to find out what all this stuff's for!" "Going at it blindly, we'd probably execute ourselves." "We've got to—" "No!" Then, more quietly—"We still have eleven hours to find a way out." time it takes us to get to the lifeboat, fly to the ship, land, stow it, get ourselves aboard, and get the big ship away from the planet. metal hall. At the other arch, where the ramp led downward, he called a "We're wearing heavy suits and bulky breathing units. We have no equipment." perhaps less broad than their own. The metal, without mark of any sort, gleamed under the combined light of the torches, unrolling out of the Metal as smooth and featureless as that on which they stood shone down silently. They moved along the metal, past unfamiliar shapes made more so by gloom and moving shadows, past doors dancing grotesquely in the The metal street ended eventually in a blank metal wall. The edge of the city—the city which was a dome of force above and a They began to retrace their steps along the metal street, back past the same dancing shapes of metal, the partitions, the odd windows, all Martin looked at the metal street lined with its metal objects and he sighed. He remembered how the dark buildings of the city looked at surface level, how the city itself looked when they were landing, and now. Idealism died in him, again and again, yet it was always reborn. But—The only city, so far as anyone knew, on the first planet they'd ever explored. And it had to be like this. Nightmares, Wass said, and Martin thought perhaps the city was built by a race of beings who at some point twisted away from their evolutionary spiral, plagued by a sort of racial insanity. No, Martin thought, shaking his head. No, that couldn't be. a faint strain through all this broad jumble, the junkpile of alien metal, which was making him theorize so wildly. Torchlight reflected from Wass' faceplate as he turned his head. "Why not?" They were like children.... "We don't know, released, what they'll do." a plant to grow in this environment, it wouldn't need much water. Maybe—" he had a vision of evil plants attacking them, growing with super-swiftness at the air valves and joints of their suits "—only the little moisture in the atmosphere." take off. Let's search awhile first. Let this be a last resort." Rodney jerked his head negatively. "No. Now, I know you, Martin. Postpone and postpone until it's too late, and the ship leaves without us and we're stranded here to eat seeds and gradually dehydrate ourselves and God only knows what else and—" He reached out convulsively and yanked a switch. looking back. "It got in and out of the city some way. Perhaps we can picking out shadowy, geometrical shapes, duplicates of the ones on the Rodney played his torch about the metal figures carefully placed about "Rodney! Stop it!" Rodney swallowed audibly. "This place scares me...." "The first time I was ever in a rocket, it scared me. I was thirteen." "This is different," Wass said. "Built-in traps—" "They had a war," Martin said. Wass agreed. "And the survivors retired here. Why?" before the war as a retreat." He turned impatiently. "How should I know?" Wass turned, too, persistent. "But the planet was through with them." "In a minute," Martin said, too irritably, "we'll have a sentient They moved slowly down the metal avenue, between the twisted shadow Martin swung his flashlight, illuminating the distorted metal shapes. expeditions to study. So will we if we don't find a way to get out." the same metal as everything else in the city, set beside the disk. The three men, clad in their suits and helmets, grouped around the tenuous, questing alien limb edged through the hatch, curling about obscuring the dimly seen backdrop of geometrical processions of strange He sighted a path parallel with the avenue above, toward the nearest

<question>:
The explorers note the metal band around the city and assume that it is there for defense.  What is ironic about the way they opt to proceed?

<options>:
A They decide to leave the city even though the defense mechanism has not worked for millions of years.  Had they gone on, they would have been rich beyond their wildest dreams.
B They do not believe that the defense mechanism will be engaged, so they venture on.
C They feel that even though the city could be defended, they do not feel that it will match the defenses they bring with them, thus proceeding.
D They become afraid that they will be attacked even though this planet has been abandoned for millions of years.

<answer>:

B