observation sentry的用法和樣例：
例句
- The working environment for guards at the observation post is very tough.
觀(guān)察哨上的哨兵工作環(huán)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.
即應設置在高大建筑物的院子中，山后，洼地或其它敵軍觀(guān)察哨或火力視野之外。
