When do many grains of sand become a pile of sand?

Which one of the following is not a good procedure to follow if you wish to avoid being rear ended by another vehicle

Why did the strike at the pullman plant in chicago become a nationwide strike?

When approaching an emergency vehicle, law enforcement vehicle, or tow truck stopped on a two-lane road with a speed limit of 20 mph or less, you are required to a. slow down to 10 mph b. slow down to 5 mph c. stop and offer assistance d. pass the vehicle in an opposing lane, if safe