hohlraum

例句：

1. 1. The soldiers dugdeep trenches to protect their position.
   士兵们挖深战壕来保护自己的位置。
2. 2.The engineers designed a complex trench system for the construction project.
   工程师们为建设项目设计了一个复杂的战壕系统。
3. 3.The enemy launched an attack from thetrench, but our troops were readyfor them.
   敌人从战壕发起了攻击，但我们的部队已经做好了准备。