Which character in Harry Potter and the Prisoner of Azkaban helped Harry rescue Hermione Granger from a troll?
Ronald Weasley
Title: Harry Potter and the Prisoner of Azkaban
Passage: Harry Potter and the Prisoner of Azkaban is the third novel in the "Harry Potter" series, written by J. K. Rowling.  The book follows Harry Potter, a young wizard, in his third year at Hogwarts School of Witchcraft and Wizardry.  Along with friends Ronald Weasley and Hermione Granger, Harry investigates Sirius Black, an escaped prisoner from Azkaban who they believe is one of Lord Voldemort's old allies.
Title: Hermione Granger
Passage: Hermione Jean Granger ( ) is a fictional character in J. K. Rowling's "Harry Potter" series.  She first appears in "Harry Potter and the Philosopher's Stone", as a new student on her way to Hogwarts.  After Harry and Ron save her from a mountain troll in the girls' toilets, she becomes best friends with them and often uses her quick wit, deft recall, and encyclopaedic knowledge to help them.  Rowling has stated that Hermione resembles herself at a younger age, with her insecurity and fear of failure.
Title: Fantastic Beasts and Where to Find Them
Passage: Fantastic Beasts and Where to Find Them is a 2001 book written by British author J. K. Rowling (under the pen name of the fictitious author Newt Scamander) about the magical creatures in the "Harry Potter" universe.  The original version purports to be Harry Potter's copy of the textbook of the same name mentioned in "Harry Potter and the Philosopher's Stone" (or "Harry Potter and the Sorcerer's Stone" in the US), the first novel of the "Harry Potter" series.  It includes several notes inside it supposedly handwritten by Harry, Ron Weasley, and Hermione Granger, detailing their own experiences with some of the beasts described, and including in-jokes relating to the original series.
Hermione Granger Harry Potter and the Prisoner of Azkaban