Why were officers posted to positions behind the lines during each battle

they where posted behind the lines during each battle because behind the trenches and lines their were shops command centers and other stuff so officers and soldiers had to stay by the trenches because they had to fight and they shouldn't just be walking around.  

Explanation: this is the answer I done this question before its not word for word but this is really close.

propriety is the answer. hope this !

explanation:

i believe the answer is d.