Which of these hotel chains is the largest by number of available rooms?

Marriott is the world's biggest hotel chain. The U.S.-based hotel chain is the world's biggest, after its merger with Starwood Hotels and Resorts in 2016. Marriott has a global presence in 110 countries, where there are over 5,700 properties spread across 30 brands, including the Sheraton brand, which is the third biggest revenue generator in the company's portfolio.

Source: Wikipedia