外星人准备攻打地球,派探子化装成地球人来打探消息。探子在中国找到一个乞丐,问他:“什么东西摸得着看不见?”乞丐觉得他烦又不给钱,摸摸后脑勺不理他。探子一看,想:嗯,他答对了,就是后脑! The aliens are ready to attack the earth and send spies to disguise themselves into Earth to find out about the news. The scout found a beggar in China and asked him: “What can’t be seen in touch?” He felt he was bothered and not giving money, and he was ignoring him when he felt it. The scout looked and thought: Well, he’s right, it’s the back of the head!