which pair of events describes a significant cause and effect that occurs in the story

So we put the horses into as much of a trot as the deep snow would allow, and before long it was evident that we were gaining on our predecessors, for the tracks grew more distinct. We hurried along, and at the end of an hour the tracks looked still newer and fresher — but what surprised us was that the number of travelers in advance of us seemed to steadily increase. We wondered how so large a party came to be traveling at such a time and in such a solitude. Somebody suggested that it must be a company of soldiers from the fort, and so we accepted that solution and jogged along a little faster still, for they could not be far off now. But the tracks still multiplied, and we began to think the platoon of soldiers was miraculously expanding into a regiment — Ballou said they had already increased to five hundred! Presently he stopped his horse and said:

“Boys, these are our own tracks, and we’ve actually been circussing round and round in a circle for more than two hours, out here in this blind desert! By George this is perfectly hydraulic!”

Then the old man waxed wroth and abusive. He called Ollendorff all manner of hard names — said he never saw such a lurid fool as he was, and ended with the peculiarly venomous opinion that he “did not know as much as a logarythm!”

The options you were given are the following:

Cause: The men become aware that they are following their own footsteps. Effect: They lose faith in Ollendorff as a guide.
Cause: The men realize they might be wandering down a sagebrush path instead of a road. Effect: The horses wander away from the group.
Cause: The men get distracted while trying to light the fire with a pistol. Effect: The men are forced to change the way they navigate.
Cause: The men lose sight of the wagon tracks as the snow continues to fall. Effect: They decide to camp and make a fire.

Events in a story can be connected in many ways. One type of relationship between events is the cause-and-effect relationship. This means that one event (the cause) causes another one to happen (the effect).

This type of relationship is present in the given passage from Roughing it. The characters led by Ollendorff, who claims to have impeccable compass-like instincts, are following what seems to be tracks of numerous people. Eventually, they realize that they are following their own footsteps. This realization (cause) causes them to lose faith in Ollendorff as a guide (effect).

This is why the first option is the correct one.