input: Text: THE HUNTED HEROES By ROBERT SILVERBERG The planet itself was tough enough—barren, desolate, forbidding; enough to stop the most adventurous and dedicated. But they had to run head-on against a mad genius who had a motto: Death to all Terrans! "Let's keep moving," I told Val. "The surest way to die out here on Mars is to give up." I reached over and turned up the pressure on her oxymask to make things a little easier for her. Through the glassite of the mask, I could see her face contorted in an agony of fatigue. And she probably thought the failure of the sandcat was all my fault, too. Val's usually about the best wife a guy could ask for, but when she wants to be she can be a real flying bother. It was beyond her to see that some grease monkey back at the Dome was at fault—whoever it was who had failed to fasten down the engine hood. Nothing but what had stopped us could stop a sandcat: sand in the delicate mechanism of the atomic engine. But no; she blamed it all on me somehow: So we were out walking on the spongy sand of the Martian desert. We'd been walking a good eight hours. "Can't we turn back now, Ron?" Val pleaded. "Maybe there isn't any uranium in this sector at all. I think we're crazy to keep on searching out here!" I started to tell her that the UranCo chief had assured me we'd hit something out this way, but changed my mind. When Val's tired and overwrought there's no sense in arguing with her. I stared ahead at the bleak, desolate wastes of the Martian landscape. Behind us somewhere was the comfort of the Dome, ahead nothing but the mazes and gullies of this dead world
  Question: Why have Val and Ron joined a mission on Mars?
  
   (A) to locate a new source of fuel
   (B) to restore Earth's depleted fuel reserves
   (C) to determine if the planet can be colonized
   (D) to identify the source of recent astronaut murders
  Answer:
output: to restore Earth's depleted fuel reserves