Read this excerpt from "Rikki-Tikki-Tavi."Nag coiled himself down, coil by coil, round the bulge at the bottom of the water-jar, and Rikki-tikki stayed still as death. After an hour he began to move, muscle by muscle, toward the jar. Nag was asleep, and Rikki-tikki looked at his big back, wondering which would be the best place for a good hold. "If I don't break his back at the first jump,” said Rikki, "he can still fight; and if he fights—Oh, Rikki!” He looked at the thickness of the neck below the hood, but that was too much for him; and a bite near the tail would only make Nag savage."It must be the head,” he said at last; 'the head above the hood; and when I am once there, I must not let go.”Then he jumped. The head was lying a little clear of the water-jar, under the curve of it; and, as his teeth met, Rikki braced his back against the bulge of the red earthenware to hold down the head.How does the protagonist move the plot forward in this excerpt?