Answer:
Rikki-tikki-tavi kills Nagina, the mother snake.
Step-by-step explanation:
'Rikki-Tikki-Tavi' is a short story and a part of The Jungle Book written by Rudyard Kipling.
The story is about the titular character, a young mongoose, who protects his human family from Nag and Nagina who are conspiring to kill all humans.
The Rising action of the story includes when Rikki-Tikki-Tavi kills Nagina, the mother snake. This event takes place in the resolution part of the plot. In the Rising Action of the story, Rikki-Tikki-Tavi finds out about Nag and Nagina. And confronts Nag, for killing the fledglings of Darzee. The rising action also consists of Rikki-Tikki-Tavi being introduced to Teddy's family, when he was rescued by the family.
Thus, the event that is NOT a part of rising action is the last option.