One day, a baby snail found that he had to carry a big and heavy shell at any time. He didn't 1 why it was, so he went up to his mother and asked, "Why was I born with a shell that grew so 2 and heavy?" His mother said, "Because we don't have 3 to hold us up. We can only move slowly, so we need a shell to 4 us. "
The baby snail asked again, "The caterpillar （毛毛虫） has no bones, and she can't move quickly either. Why can she 5 without a shell?" The mother snail answered, "That's because a caterpillar will become a butterfly. She can 6 high into the sky. The sky can protect her. "
The baby snail had one more 7 "But the earthworm moves like us. He has no bones and he won't turn into a butterfly. Why doesn't he carry a hard and heavy shell?" His mother said, "He can dig a hole and hide in the 8 , and then the earth can protect him. "
The baby snail then cried, "We are so 9 ! We have no protection from the sky or from the ground!" His mother smiled at him. "That's why we have a shell. My dear, imagine that if we don't have the shells, what will happen to you? Hot sun will dry out our bodies and we'll have nowhere to sleep. What's more, we'll die in the heavy rain. How 10 it is! We don't depend on the sky or the ground for protection. We should depend on ourselves. "
