Derrick thinks his grandfather is boring when he tells stories about being in the vietnam war. derrick doesn't want to be rude, so he nods his head and says "uh huh" and "wow" a lot. his grandfather is hurt by derrick's as he can tell derrick is not truly listening.

The answer is pseudo listening. His grandfather was hurt because Derrick is pretending that he listens to his stories but in fact, Derrick finds these so "boring". Derrick does not want to hurt his grandfather that is why he acts as if he is really listening. Pseudo-listening is the term when an individual partially or totally ignores the speaker but not act rude to avoid hurting his feelings.