Two snakes were slithering through a field. One snake turned to the other and asked, " Do you suppose we are poisonous snakes?" ZVr中国英语学习网 ZVr中国英语学习网 " I don't know", replied the other, "Why?" ZVr中国英语学习网 ZVr中国英语学习网 "Well", said the first, "I just bit my lip"ZVr中国英语学习网