Jimmy's parents got a dog from Earth. They wanted to give it to Jimmy as a pet. Jimmy still wanted to have Robutt.
Jimmy's Moon-born. His arms and legs were long and agile. He looked (thick) and stubbier with his spacesuit on, but he could handle the lunar gravity as no Earth-born human being could. Robutt didn't need a spacesuit, and had four (leg) and tendons of steel. Jimmy couldn't go wrong while Robutt was around, (trip) him when he was too near a rock, or jumping on him (show) how much he loved him, or circling around and squeaking low and scared when Jimmy hid behind a rock, when all the time Robutt knew well enough where he was.
Jimmy's father thought Robutt was just machine. It was just programmed to act the way it did. A dog was alive. The dog would really love Jimmy. Robutt was just adjusted to act as though it loved him. Jimmy didn't agree with his father. He thought Robutt wasn't an (imitate). He told his father they didn't know what was inside the dog, or what his feelings were. Maybe it was just acting, too. Jimmy held Robutt (tight). He (frown), too, and the desperate look on his face meant that he wouldn't change his mind.
