小蜗牛问妈妈:“为什么蜗牛从生下来就要背负又硬又重的壳?”妈妈说:“因为蜗牛家族身体没有骨骼支撑,只能慢慢爬,所以要用壳来保护。”小蜗牛又问,毛虫和蚯蚓都没有骨头,为什么不用背着一个壳?妈妈说,因为毛虫长大后会化成蝴蝶,会受到天空的保护;蚯蚓会钻入土中,会受到大地的保护。小蜗牛哭了,感觉自己好可怜,因为天空和大地都不保护它。蜗 A small snail asked her mother: “Why a snail born from carrying a hard and heavy shell?” “Mom said: ” Because the snail family body without bone support, can only slowly climb, so use the shell to protect. "Small snail asked, caterpillars and earthworms are not bones, why not carry a shell? Mom said, because the caterpillar grow into a butterfly, will be protected by the sky; earthworms will drill into the earth, will be protected by the earth . The little snail cries and feels miserable because neither the sky nor the earth protects it. Cochlear