A、Because they were worn out and couldn’t be worn any longer. B、Because he wanted to test his dog’s ability to get things back.

John had a pair of old shoes which had brought him much trouble, so he decided to throw them away. He went to the rubbish area outside the city and threw his old shoes into it. "Now they can bring me no trouble," he said. Then he returned home, lay down on his bed and slept. But he had a dog, and the dog often went to the rubbish area to look for food because John seldom gave food to the dog. But the dog still loved his master. The dog saw the shoes in the area and knew they were his master’s. So the dog took one of his shoes in his mouth and went back with it, and left it at his master’s bedside. Then the dog got back the other shoe in the same way. When John woke up, he saw the shoes by his bedside and was very afraid. "These shoes can walk by themselves. They must be clone away with," he thought. Then he made a large fire in front of his house and put the shoes in it. Just then a strong wind was blowing, and soon the fire made the house begin to burn. His neighbors came at once, but they could do nothing. The house was burned down, but the old shoes were saved by the dog again.