Read these sentences from the "The Final Assault." This little slope was to be our campsite. It was certainly far from flat and it was to need a lot of work on it before we could possibly pitch a tent. We carefully moved all the gear to one side and then set to work with our ice axes to remove the surface snow off a reasonably large area. Ten inches down, we struck rock, and after an hour’s work we had cleared an area about eight feet long and six feet wide. The slope underneath was made up of stones and rubble all firmly glued together with ice. This was much harder going. With the picks on our ice axes we chopped away at the slope, prizing out the separate stones and scraping away the rubble.

Which phrase best explains why the ideas in these sentences are organized as they are?

to demonstrate why their actions are important

to explain how to pitch a tent on a mountain

to create a chronological account of their work

to describe the difficulties of creating a camp