Roll-up giant United Rentals Inc. says it is exploring “a broad range of strategic alternatives...including a possible sale of the company.” The world’s largest rental company also says that CEO Wayland R. Hicks plans to retire at the company’s annual shareholder meeting on June 4. Michael J. Kneeland, executive vice president, will succeed Hicks as interim CEO. Some industry insiders speculate that United is a potential target for private-equity bidders, who have recently been snatching up rental firms in a time of healthy profits. United’s announcement comes after a string of recent sales of other national rental firms, such as Hertz, RSC, NationsRent and Neff.