Seen form the moon,the earth with water covering 70% of it's surface appears as a "blueball"
因为这是非谓语
逻辑主语是the earth,前后逻辑主语一致
所以前面从句的逻辑主语也是earth,因为地球是被看的,所以用过去分词表示被动
而现在分词表示主动
see是谓语,一句话不能有两个谓语的那也就是说Seen前面的'be'被省略了是吗？？？没有~前面没有省略任何东西如果要改成状语从句的话就是when the earth is seen form the moon,the earth with water covering 70% of it's surface appears as a "blueball"