Two friends enter a marathon. After they had been running for a while, they were passed by a tall, muscular man. "I know that guy" the first said. "He's a construction worker." A few minutes later, another racer passed them with long, loping strides. "That fellow's a doctor." Just then, ambulance sirens began to wail in the distance, and a runner sprinted by so quickly that he was just a blur. "Who was that?" asked the second friend. "Him?" the first answered. "He's a lawyer!"