What theme is found in this excerpt from Jack London's "Up the Slide"? Reaching upward the distance of a step, he brushed away the snow, and in the frozen gravel and crumbled rock of the slide chopped a shallow resting place for his foot. Then he came up a step, reached forward, and repeated the maneuver. And so, step by step, foothole by foothole, a tiny speck of toiling life poised like a fly on the face of Moosehide Mountain, he fought his upward way.

Twilight was beginning to fall when he gained the head of the slide and drew himself into the rocky bottom of the gully. At this point the shoulder of the mountain began to bend back toward the crest, and in addition to its being less steep, the rocks afforded better handhold and foothold. The worst was over, and the best yet to come!

The gully opened out into a miniature basin, in which a floor of soil had been deposited, out of which, in turn, a tiny grove of pines had sprung. The trees were all dead, dry and seasoned, having long since exhausted the thin skin of earth.

Clay ran his experienced eye over the timber, and estimated that it would chop up into fifty cords at least. Beyond, the gully closed in and became barren rock again. On every hand was barren rock, so the wonder was small that the trees had escaped the eyes of men. They were only to be discovered as he had discovered them— by climbing after them.

He continued the ascent, and the white moon greeted him when he came out upon the crest of Moosehide Mountain. At his feet, a thousand feet below, sparkled the lights of Dawson.

But the descent was precipitate and dangerous in the uncertain moonlight, and he elected to go down the mountain by its gentler northern flank. In a couple of hours he reached the Yukon at the Siwash village, and took the river-trail back to where he had left the dogs. There he found Swanson, with a fire going, waiting for him to come down.

And although Swanson had a hearty laugh at his expense, nevertheless, a week or so later, in Dawson, there were fifty cords of wood sold at forty dollars a cord, and it was he and Swanson who sold them.

A.
To be a success in life it is important to experience nature.
B.
It is important to avoid challenging situations.
C.
It is important to persevere through challenging situations.
D.
To appreciate nature you must be prepared to face challenges.