Read this excerpt from The Call of the Wild by Jack London. It was a hard day's run, up the Canon, through Sheep Camp, past the Scales and the timber line, across glaciers and snowdrifts hundreds of feet deep, and over the great Chilcoot Divide, which stands between the salt water and the fresh and guards forbiddingly the sad and lonely North. They made good time down the chain of lakes which fills the craters of extinct volcanoes, and late that night pulled into the huge camp at the head of Lake Bennett, where thousands of goldseekers were building boats against the break-up of the ice in the spring.

Why does the author most likely include this detail?

It is a part of the exposition that introduces the dogs’ personalities.
It is a part of the exposition that describes the history of the gold rush.
It is a part of the rising action that shows the progress of the journey.
It is a part of the rising action that emphasizes the challenges of sled travel.