Answer: The correct answer is c. Survival of the fittest.
Explanation: Survival of the fittest occurs when as the group of individuals of a particular species has the caracteristics or traits that allows them to be better suited or adapted to their local enviroment. The individuals of said species that lacks those specific characteristics usually goes extint.
In this case, the elephans that had long trunks with which to reach out for leaves were able to reproduce more succesfully than elephants with short trunks, which in turn went extinct.
In conclusion, the correct answer is C. Survival of the fittest.