How we cite our quotes: All quotations are from Harry Potter and the Deathly Hallows – Part 1.
Quote #1
LUPIN: What creature sat in the corner the first time Harry Potter visited my office in Hogwarts?
HARRY: Are you mad?
LUPIN: What creature?
HARRY: A Grindylow.
LUPIN: We have been betrayed. Voldemort knew you were being moved tonight. I had to make sure you weren't an imposter.
There are so many secret plots and betrayals going on in Harry's world that Lupin is super aggressive about making sure that Harry actually is Harry when they rendezvous at the Burrow after the disastrous transport that kills Mad-Eye (and Hedwig).
Quote #2
DUMBLEDORE'S DARK SECRETS REVEALED
RITA SKEETER LAUNCHES NEW BOOKDUMBLEDORE REMEMBERED BY ELPHIAS DOGE
These are two different headlines from The Daily Prophet. Elphias Doge is a friend of Dumbledore's, so he isn't out to trash or betray Dumbledore's privacy—but Rita Skeeter is a different story. She is all about violating other people's confidence and digging up their secrets (even the ones that aren't, er, true).
Quote #3
SCRIMGEOUR: "First, to Ronald Billius Weasley, I leave my Deluminator, a device of my own making in the hope that when things seem most dark, it will show him the light."
Ron probably wishes he could use his Deluminator to shed light on why exactly Dumbledore left that particular object to him. Unfortunately, Dumbledore was not overly forthcoming about his thoughts and plans in general, and his intentions here are definitely pretty mysterious. For now, anyway.