Answer:
B. They can't tell who is a civilian and who is an enemy combatant.
Step-by-step explanation:
In the book Sunrise Over Fallujah by Walter Dean Myers, the book is centered about an 18 year old US soldier named Robin but called Birdy in Kuwait where he is waiting for orders on where next to go. Eventually, he is sent to Iraq after going through confusing Rules of Engagement about who to shoot and who not to shoot.
The Civil Affairs unit which happens to be Birdy's unit is tasked with the responsibility of gaining the trust of the local Iraqis to trust the American soldiers.
Their confusion about who is a friend or foe in Iraq is characterized when they start getting remote IED attacks and do not know where it is coming from or who to trust.