article: Many rules govern drivers on American streets and highways. The most common _ are the speed limits . The speed limits control how fast a car may go.
  On streets in the city,  the speed limitis usually 25 or 35 miles per hour.On the highways between cities, the speedlimit is usually 55 miles per hour. When people drive faster than the speedlimit, a policeman can stop them. The policemen give them pieces of paper which people call traffic tickets. Traffic tickets tell the drivers how much money they must pay. When drivers receive too many tickets, they probably cannot drive for a while.
  The rush hour is when people are going to work or going home from work. At rush hour there are many cars on the streets and traffic moves very slowly. Nearly all American cities have rush hours. Drivers do not get tickets very often for speeding during the rush hours because they cannot drive fast.
question: The passage is mainly about  _  .
options: rush hours American drivers traffic rules traffic policemen