Answer:
This best illustrates flashbulb memory.
Explanation:
Flashbulb memory can be understood as a "snapshot" of a certain moment in which something surprising or really emotional was heard. It is related to biographical events and tends to be extremely detailed and can be exceedingly vivid for the individual.
In this case, Joshua is experiencing a the flashbulb memory since he remembers his feelings and exactly what he was doing the moment he heard of his grandfather's death.