undefended building

例句：

1. 1. The undefended building was a target for burglars.
   这座未受保护的建筑成为了窃贼的目标。
2. 2. The undefended area was left vulnerable to natural disasters.
   这个未被防御的区域容易受到自然灾害的影响。
3. 3.The security guards were posted outside the undefended gate.
   保安人员被部署在未被防御的大门外。