Here is a passage from a study published by the National Highway Traffic Safety Administration in 2007. "The National Occupant Protection Use Survey (NOPUS) is the only probability-based survey of driver cell phone use in the United States. The survey observes usage as it actually occurs at a random selection of roadway sites, and so provides the best tracking of the extent to which people in this country are using cell phones while driving." NOPUS observed 43,000 drivers in this study. Identify the population and sample in the study. O Population: 43,000 Drivers in this study; Sample: Drivers at the randomly selected roadway sites. O Population: Drivers in the United States; Sample: 43,000 Drivers at randomly selected roadway sites. O Population: U.S. drivers; Sample: 43,000 Drivers at randomly selected roadway sites. O Population: U.S drivers; Sample: 43,000 drivers using their cell phones