For thirty years, Johnson arrived at work at 9A.M. exactly. He never missed a day and was never late. However, on one particular day, 9A.M. passed without Johnson's arrival, it caused a sensation  . All workers stopped and wait, and the boss himself looked at his watch and complained. Finally, exactly at ten, Johnson turned up, clothes dusty and torn, his face hurt and bruised , his glasses bent. He limped painfully to the time clock, struck in with a strong fist, and said, knowing that all eyes were upon him, "I fell and rolled down two flights of stairs in the subway and nearly killed myself." But the boss said, "And to roll down two flights of stairs took you a whole hour?" How long did Johnson work in the company?
9 years. 10 years. 20 years. 30 years.