The structural element used in both stories is the inclusion of a flashback about an event (option D) The use of it might be to portray each protagonist´s experience, in the case of "Ambush" the narrator situates his experience in <span>Vietnam between related events that take place after the war. And in "facing It" the narrator recalls the Vietnam War. </span>
A distraction for the students may have been it simply wasn't an interesting enough or grasping topic for the students, or even the way he was dressed which was kind of flashy or really eye catching could have focused thier attentions elsewhere. Hope This Helps