Answer:
The statement that best describes the purpose of the excerpt is the third one: to explain how balance came to exist in the natural world.
Step-by-step explanation:
In this excerpt, the speaker is explaining how natural balance works, how nature works things out in order to create balance between things. In this case, the speaker talks about a pair of twins -one right handed and the other left handed- one creates the plant eating animals, and the other creates the meat eating animals. This keeps the world balanced, not every animal eats meat, not every animal eats plants, so there will always be plants and meat because not every animal eats the same and this makes the world function well.