observation sentry的用法和樣例：
例句
- The working environment for guards at the observation post is very tough.
觀察哨上的哨兵工作環境很艱苦。 - This means situating in the courtyard of a large building, behind a hill, in a depression, or some other place where the natural terrain protects the team from observation or fire.
即應設置在高大建築物的院子中，山後，窪地或其它敵軍觀察哨或火力視野之外。
