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 . Given these facts, injury of the lungs can be caused by what among the following options:
- running
 - wind and erosion
 - breathing
 - cigarettes
 - Pesticides
 - bacterial infection
 - smoking cigarettes
 - foggy air


 

      bacterial infection   