You are presented with the question "injury of the lungs can be caused by what" and the following answer choices: 
- running
 - wind and erosion
 - breathing
 - cigarettes
 - Pesticides
 - bacterial infection
 - smoking cigarettes
 - foggy air

Now knowing that pneumonia may be caused by an infection or injury of the lungs and common bacterial pneumonia can be caused by Streptococcus pneumonia or Klebsiella pneumonia , choose the best answer.


 

      bacterial infection   