Read this excerpt from Susan Butcher and the Iditarod Trail. Then, abruptly, Balto stopped. Kaasen shouted at him to go on, but the dog would not move. Kaasen ran forward to see what was wrong. Balto was standing in several inches of icy water. They were on the bank of the Topkop River, and the ice below was beginning to give way. Had they continued, the team and sled would have pitched forward into the river. Balto knew what he was doing. As soon as Kaasen dried the dog's feet, Balto made a turn and led the team around the river and back to the trail.

What can a reader infer based on the information in the excerpt?

Sled dogs like Balto depended completely on mushers to make the decisions on a journey.
Sled dogs like Balto were stubborn and had difficulty following directions from their mushers.
Sled dogs like Balto used their natural animal instincts to make intelligent decisions.
Sled dogs like Balto lost the use of their natural animal instincts when they lived with people.