You are presented with the question "Toxic carbon monoxide is produced by what?" and the following answer choices: 
- gasoline engines
 - Electric generators
 - electric cars
 - electricity
 - solar panels
 - cigarettes
 - an engine
 - ionization

Now knowing that using a gasoline engine requires burning gasoline and and, of course, burning of gasoline produces toxic carbon monoxide, choose the best answer.


 

 gasoline engines        