Read this excerpt from Susan Butcher and the Iditarod Trail. On January 29, Edgar Nollner waited in a dark cabin at Whiskey Creek, close to the halfway point. Suddenly he sat up. Bells! Was he hearing things? He ran to the window and found that it was Bill McCarty, who had tied sleigh bells to his dogs, coming in from the Ruby relay cabin. Mushers, either by choice or in some towns by law, often tied bells on their lead dogs to warn people they were coming up behind them. Edgar had not expected to hear Bill's bells for several days, but he wasted no time. He took the serum and started north along the frozen Yukon River.

Which conclusion can be formed based on the information in the excerpt?

Near the halfway point, the movement of the serum by dog teams was going worse than expected.
Near the halfway point, the plan to deliver serum by dog teams was considered a mistake.
Near the halfway point, the mushers tied bells on the lead dogs to warn of their arrival.
Near the halfway point, the movement of the serum by dog teams was going better than expected.