This is the part of the story where the dogs wouldn't budge and pull the sled, because Hal, Charles, and Mercedes were inexperienced and didn't know what they were doing. Eventually, they ended up following the advice to lighten the load.
This is the end of Chapter Five, where Mercedes and the dogs fell through the ice because she did not listen to John Thornton´s advice to not go on the ice, which was thinning out because of the weather. She is therefore refusing to adapt and decided to do it anyway. Page 69
This is the scene where people are offering to help Hal and Charles with the dogs and the sled. These people are fit to survive because they know what they are doing, and they are providing advice.
"They did not know how to do anything, and as the days went by it became apparent that they could not learn." - page 59 This quote explains how the three new owners were obviously very inexperienced, refused to listen to advice, and especially could not adapt to the new environment.
"If you strike that dog again, I'll kill you," he at last managed to say in a choking voice. -Page 68 This quote shows that John Thornton knows and cares about taking care of wild dogs. He doesn't want the dogs to suffer, and they need to rest if they want to travel a far distance.
"And they told you true," John Thornton answered. "The bottom's likely to drop out at any moment."-Page 66 John Thornton was trying to help out Mercedes and the men, but the refused to accept his advice. Thus, John was fit to survive and the others were not.