Mom: Because our bodies have no bones to support, we can only climb, but we can't climb fast. So we need the protection of this shell!
Snail: Sister Caterpillar has no bones and can't climb fast. Why doesn't she have to carry this hard and heavy shell?
Mom: Because sister caterpillar can become a butterfly, the sky will protect her.
Snail: but brother earthworm can't climb fast without bones, and he won't become a butterfly. Why doesn't he carry this hard and heavy shell?
Mom: Because Brother Earthworm can drill soil, the earth will protect him.
The little snail began to cry: we are so poor that the sky is unprotected and the land is unprotected.
Mother snail comforted him: so we have shells! We don't rely on the sky, we don't rely on the ground, we rely on ourselves.