Carpooling decreases the amount of cars used to travel to a place, and arrange carpools to conserve fuel. Given these facts, decreasing what during travel likely conserves fuel among the following options:
- the energy of the car
 - air mass over Earth's surface
 - the amount of cars used
 - the size of the wheels
 - the amount of water used
 - kinetic energy
 - preventing heat transfer
 - energy usage


 

   the amount of cars used      