How is the title "Ambush" ironic?

Select the best answer from the choices provided.
A.
Instead of the enemy engaging in ambush, the common guerilla method, the narrator himself commits the ambush.
B.
The enemy solider was unarmed and therefore could easily have been captured and held as an enemy hostage instead of ambushed.
C.
The title suggests that the narrator will be ambushed and forced to kill, when in actuality, the narrator chooses to kill.
D.
The title suggests a surprise attack, which is exactly what occurs during the story's flashback to the Vietnam War.