question:  What is the most precious commodity on the moon?
context: 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 that died when the meteor was created fell on Earth before the first lungfish ventured from the sea. In its last instant, the meteor fell on the Moon. The shaft tried to tie itself into a knot, and the blades, damaged and undamaged were spit through the casing. The shadow line between day and night could be seen from the Moon to be drifting across Australia. Once he followed a stampede to Yellow Crater, where he thought for a while that he had a fortune in chromium. 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 dark again, and the search for him, if it ever began, could not begin for thirteen more days. By the light of this, he reinspected the steam system, and found about three gallons of water frozen in the condenser. It was three days' supply of water, if it had been carefully used. It was one day's supply if used wastefully. This was to allow the air-conditioning system to function properly, and to prevent air loss in case of the highly improbable meteor damage. For example, because of an order of his stating that there would be no alcoholic beverages within the survey building, the entire survey was assured of a constant supply of home-made, but passably good liquor. Morning to him had no meaning at all, but he thought in the strictest sense that it would be morning on the Moon for another week. It was used mostly, from sun-up to sun-down, to supplement the nuclear power plant. "Meteor shower," Cowalczk answered, "and that's not half of it.
output:  Water
options:  Water  Oxygen  Natural gas  Chromite ore