Final answer:
Professor Lockhart initiates the Dueling Club at Hogwarts during Harry Potter's second year, revealing Harry's ability to speak Parseltongue during a duel. Option C.
Step-by-step explanation:
The Dueling Club at Hogwarts during Harry's second year was started by Professor Lockhart. This event is a notable part of Harry Potter's experiences in his second year as depicted in "Harry Potter and the Chamber of Secrets."
Professor Gilderoy Lockhart, the Defense Against the Dark Arts teacher at that time, initiates the club with the intention of teaching students how to defend themselves.
However, he is largely inept and the club does not go as planned, especially when an actual duel between Harry and Draco Malfoy reveals Harry's ability to speak Parseltongue.
So Option C is the correct answer.