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

<passage>:
"Can't tell yet. They spotted the tractor from the satellite The meteor, a pebble, a little larger than a match head, traveled through space and time since it came into being. The light from the star In its last instant, the meteor fell on the Moon. It was impeded by have been formed by steam some time, because there's a floor of ice in all of 'em. "The idea didn't come all at once, it took a long time for me to remember that water is made out of oxygen and hydrogen. When I "It runs an electric current through water, lets the oxygen loose in the The shadow line between day and night could be seen from the Moon to be When he was flush, he would prospect for a couple of weeks. Once he followed a stampede to Yellow Crater, where he thought for a while that he had a fortune in chromium. The chromite petered out in a month and a claim." "Claim?" the first landing on the Moon. "Sure, man, I've thousands of tons of water here. It's the richest mine on the Moon!" THE END position. "Batteries must be dead," he told himself. "What batteries?" he asked. "There're no batteries in here, the power comes from the generator." of water frozen in the condenser. The condenser, like all condensers, was a device to convert steam into water, so that it could be reused in the water in the condenser began to boil. This boiling lowered the freezing the water in the tank. the shut-off valves. If there was any water in the boiler, it would operate the engine that drove the generator. The water would condense in the pump wasn't blocked by ice, it would return the water to the boiler. drinking water into a pipe that led to the boiler, and resealed the water that he had poured into the boiler quickly turned into steam, and "The water, man," he said, "there is not enough to melt the ice in the ice in the condenser, and the water pump began to function. It was an incredibly brilliant disk in a black sky. The stars next to the sun shone as brightly as though there were no sun. They might have appeared to waver slightly, if they were behind outflung corona flares. furnace was a rough parabola of mirrors used to focus the sun's heat on anything that it was desirable to heat. It was used mostly, from sun-up to sun-down, to supplement the nuclear power plant. "They went out about an hour ago," she answered, "I suppose that's what Nobody answered. They could all see the Moon under their feet. Small craters overlapped and touched each other. There was—except in the that didn't contain a crater at least ten inches across, there was not a square inch without its half-inch crater. Nearly all of these had been made millions of years ago, but here and there, the rim of a crater covered part of a footprint, clear evidence that it was a recent one. found that the light reflected from the small ray that peered into the cave door lighted the cave adequately. He tapped loose some white crystals on the cave wall with his geologist's hammer, and put them into a collector's bag. "A few mineral specimens would give us something to think about, man. These crystals," he said, "look a little like zeolites, but that can't be, zeolites need water to form, and there's no water on the Moon." He chipped a number of other crystals loose and put them in bags. One of them he found in a dark crevice had a hexagonal shape that puzzled him. One at a time, back in the tractor, he took the crystals out of the bags and analyzed them as well as he could without using a flame which would waste oxygen. The ones that looked like zeolites were zeolites, all right, or something very much like it. One of the crystals that he thought was quartz turned out to be calcite, and one of the ones that he was sure could be nothing but calcite was actually potassium nitrate. "Well, now," he said, "it's probably the largest natural crystal of potassium nitrate that anyone has ever seen. Man, it's a full inch across." All of these needed water to form, and their existence on the Moon puzzled him for a while. Then he opened the bag that had contained the unusual hexagonal crystals, and the puzzle resolved itself. There was nothing in the bag but a few drops of water. What he had taken to be a type of rock was ice, frozen in a niche that had never been warmed by the sun. The sun rose to the meridian slowly. It was a week after sunrise. The stars shone coldly, and wheeled in their slow course with the sun. Only around until Earth was nearly dark, and then the rim of light appeared on the opposite side. For a while Earth was a dark disk in a thin halo, move around Earth. The continents drifted across the dark disk and into the crescent. The people on Earth saw the full moon set about the same tirade, "but it's not. The union it is that says who I can hire. The union it is that says how much I must pay, and how large a crew I need. And then the Commission ..." The word seemed to give Jones an unpleasant "The nickel, man, the tons of nickel worth a dollar and a half on Earth, and not worth mining here the low-grade ores of uranium and vanadium, they need these things on Earth, but they can't get them as long as it isn't worth the carrying of them. And then, of course, there's the water Both men fell silent for a while. Then Jones spoke again: "Have you seen our friend Evans lately? The price of chromium has gone up, and I think he could ship some of his ore from Yellow Crater at a profit." "He's out prospecting again. I don't expect to see him until sun-down." The sun was halfway to the horizon, and Earth was a crescent in the sky when Evans had quarried all the ice that was available in the cave. The thought grew on him as he worked that this couldn't be the only such chipping, he could locate small bubbles up to an inch in diameter, each one with its droplet of water. The average was about one per cent of the volume of each bubble filled with ice. mound of lava. It was rounded on top, and it could easily be the dome of building, a gray concrete structure a quarter of a mile distant. "It would be pretty bad if they clogged up some night." was about half full, the water began to run nearly clear. An electric the water. It neither needed nor had much strength. ruptured. A stream of mud gushed out and boiled dry on the face of the They could see the trickle of water from the discharge pipe. The motor "Water's stopped. Give us some pressure, we'll see if it holds." Cowalczk and Lehman opened the valve again. Water spurted out, and PROSPECTOR FEARED LOST ON MOON McIlroy released a statement today that Howard Evans, a prospector is missing and presumed lost. Evans, who was apparently exploring the Moon in search of minerals was due two days ago, but it was presumed that he was merely temporarily delayed. Evans began his exploration on August 25th, and was known to be by the fact that Evans is lost on the part of the Moon which is now never say a word about any forebodings." "Well, happen I might have a bit of Welsh second sight about me, and it tells me that Evans will be found." rocket would be needed in the search." The light from Earth lighted the Moon as the Moon had never lighted Earth. The great blue globe of Earth, the only thing larger than the stars, wheeled silently in the sky. As it turned, the shadow of sunset crept across the face that could be seen from the Moon. From full Earth, are clouded over. Anyway the satellite observatory will be in position finding him. It began to dawn on McIlroy that nearly the whole

<question>:
What clue proves the natural existence of water on the moon?

<options>:
A The ability to distill alcohol
B Increase of meteor activity
C Humans are able to survive for long periods of time
D The presence of specific minerals

<answer>:

D