5/10, one reason being clarity:
A: What's an NPC?
B: It stands for non-player-character.
A: So, everything that's not a player-character. Like my sword?
B: No, it means every character that doesn't have a player.
A: Who plays the character if it doesn't have a player?
B: The DM.
A: So the troll we just killed is an NPC? The DM played it.
B: No, it's a monster. NPCs have a "personal name and distinct personality."
A: NPCs aren't monsters, then.
B: Well, an NPC is a monster, too. It just has a name.
A: Huh. What's a monster?
B: "A creature controlled by the GM."
A: Shucks. I wanted to cast Charm Monster on Steve's character.
B: You can, I guess. Charm Monster affects a "creature."
A: Just to be safe, what's a creature?
B: Um . . . "any being in the game."
A: "Being." Like any living being?
B: "Being" isn't in the glossary. I don't think it has to be living. Like a golem, or a skeleton.
A: Whoa! So I can charm the troll we just killed, and it would have to be Friendly to me?
B: I guess. You're overthinking this.