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

<passage>:
THE MOONS OF MARS [Transcriber's Note: This etext was produced from Galaxy Science Fiction September 1952. Extensive research did not uncover any evidence that of course, Martians. But this one did! He seemed a very little boy to be carrying so large a butterfly net. He swung it in his chubby right fist as he walked, and at first glance you The first was that he was a Martian little boy. You could be very sure of that, for Earth little boys have earlobes while Martian little boys do not—and he most certainly didn't. The second was the tune he whistled—a somehow familiar tune, but one "'The Calm'," he said in a sober, little-boy voice. "The what He nodded grave agreement. "Been after butterflies, I see. I'll bet you didn't get any. This is the wrong season." original mine-workings made many years ago by the early colonists. It Back in those days, to be a colonist meant to be a rugged individual. And to be a rugged individual meant to not give a damn one way or another. And to not give a damn one way or another meant to make one hell of a mess on the placid face of Mars. There had not been any gold found, of course, and now, for the most part, the mining shacks so hastily thrown up were only fever scars were still occupied, like the one into which the Martian boy had just disappeared. So his I answered: "As a matter of fact, I don't want to see you at all. I that I was interested in. The little Martian boy, I mean." been bright, moist marbles glued above her cheeks. She said one word only: "Well?" "Nothing," I answered. "Except that Martians are supposed to be tone-deaf, aren't they? It's something lacking in their sense of hearing. So when I heard this little boy, and saw he was a Martian, and "I would like to speak to the Martian lady," I said. "There isn't any Martian lady." Her eyes were telling me that the little Martian boy wasn't a little Martian boy at all, that he was cross-breed, a little chap who had a Martian father and a human, Earthwoman mother. It was a startling thought, for there just aren't any such mixed marriages. Or at least I had thought there weren't. Physically, spiritually, mentally, or by any other standard you can think of, compared to a human male the Martian isn't anything you'd want around inside her. "There isn't anything to be ashamed of," I said gently. "Back on Earth there's a lot of mixtures, you know. Some people even claim there's no such thing as a pure race. I don't know, but I guess we all started somewhere and intermarried plenty since." everything, now that...?" I stopped. I wanted to ask her if she was starving by slow degrees and needed help. Lord knows the careworn look about her didn't show it was luxurious living she was doing—at least not lately. "Look," I said suddenly. "Would you like to go home to Earth? I could fix—" But that was the wrong approach. Her eyes snapped and her shoulders stiffened angrily and the words that ripped out of her mouth were not coated with honey. "Get the hell out of here, you fool!" "Wanted, isn't he?" He nodded. "But a lot of good that'll do. He's holed up somewhere back on Earth." "No," I said. "He's right here. I just saw him." " He cut me off. His hand darted into his desk drawer and pulled out an Authority Card. He shoved the card at me. He growled: "Kill or capture, I'm not especially fussy which. Just get named Harry Smythe. Understandably, Mr. Smythe did not produce himself on a silver platter. was doing it with mirrors, for on Mars an Authority Card is the big more than a ghoul, you don't. Not finding him wasn't especially alarming. What was alarming, though, was not finding the Earthwoman and her little half-breed Martian son when I went back to the tumbledown shack where they lived. It was empty. She had moved fast. She hadn't even left me a note saying Reservation, where the Martians still try to act like Martians. to the two moons. At times like this you want to leave the Martians put on centuries ago by the ancient aborigines of North America. There was one important exception, however. Instead of a central fire, the Martians dig a huge circular trench and fill it with dried roots of the belu tree and set fire to it. Being pitch-like, the gnarled fragments thought before, that this is the one thing the Martians can still do The Martian turned, went away from the half-light of the circle. He led Wahanhk is an old Martian. I don't think any Martian before him has ever lived so long—and doubtless none after him will, either. His leathery, almost purple-black skin was rough and had a charred look about it, and up around the eyes were little plaits and folds that had the appearance of being done deliberately by a Martian sand-artist. "Power sign of the Earthmen," he muttered. "Not necessarily," I said. "I'm not here for trouble. I know as well as you do that, before tonight is finished, more than half of your men moderated in tempo. It was like the throbbing—or sobbing, if you prefer—of the old, old pumps whose shafts go so tirelessly down into the planet for such pitifully thin streams of water. "I'm looking for an Earthwoman," I said. "This particular Earthwoman took a Martian for a husband." Martian features. Or, if you want to turn it around and look at the it was simply blank. "Why?" moment before he handed it back. "I have never seen this Earthman," he said. I nodded. "For murder." "Murder." He spat the word. "But not for the murder of a Martian, eh? Martians are not that important any more." His old eyes hated me with an intensity I didn't relish. "You said that, old man, not I." curled backward around it. "That's considered bad luck," I said. I ignored that. "Why did you pull out of that shack? I told you you had If that meant anything to her, I couldn't tell. In the flickering light from the fires, subtle changes in expression weren't easily detected. "Why should I care about an Earthman? My husband was a Martian. And he's dead, see? Dead. Just a Martian. Not fit for anything, like all Martians. Just a bum who fell in love with an Earthwoman and had the guts to marry her. Do you understand? So somebody murdered him for it. Ain't that pretty? Ain't that something to make you throw back your small, thin shoulders. And I knew then the reason for old Wahanhk's bitterness when he had said to me, "But not for the murder of a Martian, eh? Martians are not that important any more." What I said then probably sounded as weak as it really was: "I'm sorry, of speed and savagery combined and those who moved to its frenetic I looked down again at the woman. "Your little boy and his butterfly net," I said softly. "In a season when no butterflies can be found. What was that for? Was he part of the plan, too, and the net just the alibi that gave him a passport to wander where he chose? So that he and he knew it would be safe, he was going to stake a claim and go after it. For us. For the three of us." I sighed. There wasn't, isn't, never will be any gold on this planet. But who in the name of God could have the heart to ruin a dream like choice. And I thought I knew the reason for his going.

<question>:
Why did humans colonize Mars?

<options>:
A To look for Martians.
B Earth was too hot to live on due to climate change.
C To mine for gold.
D Earth was overpopulated.

<answer>:

C