 Complete the following phrase:  The 2011 FIA Formula One World Championship was the 65th season of FIA Formula One motor racing. The original calendar for the 2011 Formula One World Championship consisted of twenty rounds, including the inaugural running of the Indian Grand Prix before the cancellation of the Bahrain Grand Prix. Pirelli returned to the sport as tyre supplier for all teams, taking over from Bridgestone, marking their return to Formula One for the first time since the 1991 season. Red Bull Racing was the reigning Constructors Champion. Red Bull Racings Sebastian Vettel was the defending Drivers Champion, one of five World Champions appearing on the grid. Vettel won his second World Championship at the 