4. A Dog's Tale
You have three dogs:
Beagle = Kerrie
Collie = Lassie
Terrier = Amber
No dog's name begins with the same letter as the owner's name. So Louis can't own the Collie. He can't own the Beagle either, since the question says the Beagle has a mistress, and Louis is a boy. So Louis has to own the Terrier.
Karen can't own the Beagle, Kerrie, since both names begin with K. So she has to own the Collie.
That means Alice own the Beagle.