听力原文： A double-decker Amtrak train derailed in the summer heat outside Washington on Monday, injuring 90 people, about 30 of them seriously, authorities said. The National Transportation Safety Board in New York sent a team of investigators, and an expert said they would probably try to determine whether the heat had caused the track to buckle. Temperatures were in the mid-90s. The train, en route from Chicago to the nation's capital with 173 passengers and crewmembers, jumped the tracks 10 miles from its destination at about 1: 55 p. m. , authorities said. A row of double-decker Superliner cars lay on its side next to big trees that were smashed to pieces. six people were trapped in the cars, but all were freed within an hour.How many of the passengers have been injured in the train accident?A．30.B．90.C．120.D．6.