Passage: RMS Queen Mary 2 (also referred to as the QM2) is a transatlantic ocean liner. She is the largest ocean liner ever built, having served as the flagship of the Cunard Line since succeeding the Queen Elizabeth 2 in 2004. As of 2019, Queen Mary 2 is the only passenger ship operating as an ocean liner.The new ship was named Queen Mary 2 by Queen Elizabeth II in 2004 after the first RMS Queen Mary of 1936. Queen Mary was in turn named after Mary of Teck, consort of King George V. With the retirement of Queen Elizabeth 2 in 2008, Queen Mary 2 is the only transatlantic ocean liner in line service between Southampton, England, and New York City, United States, operating for a part of each year. The ship is also used for cruising, including an annual world cruise.She was designed by a team of British naval architects led by Stephen Payne, and was constructed in France by Chantiers de l'Atlantique. At the time of her construction, Queen Mary 2 held the distinctions of being the longest, at 1,131.99 ft (345.03 m), and largest, with a gross tonnage of 148,528 GT, passenger ship ever built. She no longer held this distinction after the construction of Royal Caribbean International's 154,407 GT Freedom of the Seas (a cruise ship) in April 2006, but remains the largest ocean liner ever built.

Question: Which ship is the only passenger ship that operates as an ocean liner?
RMS Queen Mary 2