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

<passage>:
That's just line! Is Evans—?" learn the most fundamental things. Like when there's no use trying—when it's time to give up because it's hopeless.... Evans was carrying a block of ice into the tractor when he saw the "... And I don't know how long I sat there after I found the water." He looked at the Goldburgian device he had made out of wire and tubing. remember that water is made out of oxygen and hydrogen. When I remembered that, of course, I remembered that it can be separated with electricity. So I built this thing. room, and pipes the hydrogen outside. It doesn't work automatically, of Evans, who had no watch, thought of the time as a quarter after course, so I run it about an hour a day. My oxygen level gauge shows how hundred and fifty thousand dollars. Fifty thousand was paid for. The rest was promissory notes and grubstake shares. When he was broke, which was usually, he used his tractor to haul uranium ore and metallic sodium "I don't need rescuing, man," Evans said. "You might let me have some food," Evans continued. "I'm getting short of that. And you might have someone send out a mechanic with parts to he had a fortune in chromium. The chromite petered out in a month and a half, and he was lucky to break even. "Sure, man, I've thousands of tons of water here. It's the richest mine on the Moon!" sixteen days. When he saw the wrecked turbine, he knew that he wouldn't make it. By careful rationing, he could probably stretch his food out to more than a month. His drinking water—kept separate from the water in the reactor—might conceivably last just as long. But his oxygen was too carefully measured there was a four-day reserve. By diligent conservation, he might make it last an extra day. Four days reserve—plus one is five—plus sixteen days normal supply equals twenty-one days to live. In seventeen days he might be missed, but in seventeen days it would be for thirteen more days. At the earliest it would be eight days too late. "Well, man, 'tis a fine spot you're in now," he told himself. "Let's find out how bad it is indeed," he answered. He reached for the light switch and tried to turn it on. The switch was already in the "on" position. "Batteries must be dead," he told himself. "What batteries?" he asked. "There're no batteries in here, the power comes from the generator." "Why isn't the generator working, man?" he asked. He thought this one out carefully. The generator was not turned by the main turbine, but by a small reciprocating engine. The steam, however, came from the same boiler. And the boiler, of course, had emptied itself "The condenser!" he shouted. He fumbled for a while, until he found a small flashlight. By the light of this, he reinspected the steam system, and found about three gallons 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 temperature, and the condenser demonstrated its efficiency by quickly freezing the water in the tank. Evans sealed the turbine from the rest of the steam system by closing water that he had poured into the boiler quickly turned into steam, and the steam turned the generator briefly. Evans watched the lights flicker and go out, and he guessed what the "The water, man," he said, "there is not enough to melt the ice in the the boiler. It was three days' supply of water, if it had been carefully used. It was one day's supply if used wastefully. It was ostentatious luxury for a man with a month's supply of water and twenty-one days to live. was passing through them. This was to allow the air-conditioning system to function properly, and to prevent air loss in case of the highly improbable meteor damage. McIlroy thought that on the whole, he was disobeying his own orders no more flagrantly than anyone else in the accepted this without thinking about it. He had fallen into the habit of After the sun rose, Evans returned to the lava cave that he had been THE END 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 McIlroy noticed that his friend's glass was empty, and he quietly filled 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 we haven't got. We could afford to bring more water for more people, and set up more distilling plants if we had the money from the nickel. "Even though I say it who shouldn't, two-eighty a quart is too much to pay for water." "Have you seen our friend Evans lately? The price of chromium has gone "Well, if I don't see him, you let him know about the chromium." "Anything to help another Welshman, is that the idea?" "Well, protection it is that a poor Welshman needs from all the English 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 a bubble. Suddenly, Evans noticed that the gauge on the oxygen tank of his suit was reading dangerously near empty. He turned back to his tractor, moving as slowly as he felt safe in doing. Running would use up oxygen too fast. He was halfway there when the pressure warning light went on, and the signal sounded inside his helmet. He turned on his ten-minute reserve supply, and made it to the tractor with about five minutes left. The air purifying apparatus in the suit was not as efficient as the one in the tractor it wasted oxygen. By using the suit so much, Evans had already shortened his life by several days. He resolved not to leave the tractor again, and reluctantly abandoned his plan to search for a large bubble. "Because I say so," Cowalczk shouted, surprised at his outburst and ashamed of it. "Boiler scale," he continued, much calmer. "We've got to clean out the boilers once a year to make sure the tubes in the reactor don't clog up." He squinted through his dark visor at the reactor the water. It neither needed nor had much strength. shaft. It's slipping every time the valve closes. There's not enough power in it to crush the scale." "Twenty pounds," Cade answered after a couple of minutes. what happens." "Eight hundred pounds," Cade said, after a short wait. "Think we weren't worried?" Lehman asked. "And it's not over." "What?" Cade asked. "Oh, you mean the valve servo you two bashed up?" "No," said Lehman, "I mean the two thousand gallons of water that we lost." "Two thousand?" Cade asked. "We only had seven hundred gallons reserve. How come we can operate now?" "We picked up twelve hundred from the town sewage plant. What with using the solar furnace as a radiator, we can make do." "Oh, God, I suppose this means water rationing again." "You're probably right, at least until the next rocket lands in a couple of weeks." is missing and presumed lost. Evans, who was apparently exploring Evans began his exploration on August 25th, and was known to be carrying several days reserve of oxygen and supplies. Director McIlroy has expressed a hope that Evans will be found before his oxygen runs out. it is believed he was carrying only short-range, intercommunications equipment. Nevertheless, receivers are ... "Like as not, you're right," McIlroy replied, "but if I know Evans, he'd tells me that Evans will be found." this banker, who had never met Evans, was losing so much sleep about

<question>:
Why does Evans give up his drinking water?

<options>:
A Using the water is the only way for his transportation to work
B He knows he will be able to find more soon in one of the caves
C He knows his rescuers will come find him and bring water
D He knows he does not have enough to survive so he uses it to save his equipment

<answer>:

A