You are presented with the question "What can be a major threat to health?" and the following answer choices: 
- bicycling
 - using a car
 - smoking
 - skateboarding
 - viruses
 - Dehydration
 - influenza
 - doctors

Now knowing that using a car causes pollution and air pollution Air pollution is a major threat to health, choose the best answer.


 

  using a car       