Answer:
In the novel It by Stephen King, the word which describes the tone in this excerpt best is nostalgic.
Nostalgic refers to the sentiments or affections which are related to the past, specifically for a place or periods relating to a happy personal association.
In the above excerpt line which depicts nostalgic affection is
“The energy you drew on so extravagantly when you were a kid, the energy you thought would never exhaust itself—that slipped away somewhere between eighteen and twenty-four,”
Richie gets nostalgic when he enters the room and feel the energy that he used to as a kid.
Step-by-step explanation: