Unit 3 SecurityText A Years ago in America, it was customary for families to leave their doors unlocked, day and night. In this essay, Greene regrets that people can no longer trust each other and have to resort to elaborate security systems to protect themselves and their possessions. 许多年前，在美国，家家户户白天黑夜不锁门是司空见惯的。在本文中，格林叹惜人们不再相互信任，不得不凭借设计精密的安全设备来保护自己和财产。The Land of the Lock Bob Greene 锁之国1In the house where I grew up, it was our custom to leave the
