小蜗牛问妈妈:“为什么我们生下来就要背负这个又硬又重的壳呢?”妈妈说:“因为我们的身体没有骨骼的支撑,只能爬,又爬不快。”“毛虫姐姐没有骨头,也爬不快,为什么她不用背这个又硬又重的壳呢?”“因为毛虫姐姐能变成蝴蝶,天空会保护她。”“可是蚯蚓弟弟没有骨头,也爬不快,也不会变成蝴蝶,他为什么不背这个又硬又重的壳呢?”“因为蚯蚓弟 A small snail asked her mother: ”Why do we have to bear this hard and heavy shell?“ ”My mother said: “ Because our body is not supported by the bones, can only crawl and climb unpleasant. ”Caterpillar sister does not bones, but also climb unpleasant, why she did not back this hard and heavy shell?“ ”Because the caterpillar sister can become a butterfly, the sky will protect her.“ ”But earthworm brother no bones, Also crawling unhappy, it will not become a butterfly, why does he not back this hard and heavy shell? “” Because earthworm brother