How does Teddy’s father move the plot forward in "Rikki-Tikki-Tavi"? He shows Rikki-tikki how to fight Nag and Nagaina. He kills Nag after Rikki-tikki corners him in a water jar. He tells Rikki-tikki that he overheard the cobras’ plan. He comforts Teddy and offers Rikki-tikki some food.