从一则真实的故事说起在瑞士日内瓦湖上的山脉中有一条很长的汽车隧道。隧道东出口再往前400米可以俯瞰整个日内瓦湖,也因此每天都会有成百上千的游客流连于此。出于安全考虑,政府在隧道的入口处放置了一块警示牌:前有隧道,请打开车头灯。但这一警示牌却常常毁了游客的好心情,因为总有些人在准备返回时才 Speaking from a real story, there is a long tunnel of cars in the mountains above Lake Geneva in Switzerland. The east exit of the tunnel, which is 400 meters further down the lake, also allows hundreds of tourists to hang around every day. For security reasons, the government placed a warning sign at the entrance to the tunnel: a tunnel in front of it, open the headlights. However, this warning sign often ruins the good mood of tourists, because when some people are preparing to return