Pneumonia may be caused by an infection or injury of the lungs, and streptococcal pneumonia is caused by the bacteria Streptococcus pneumoniae. Given these facts, what can make lungs more at risk for infection by streptococcus among the following options:
- Allergies
 - bacteria
 - Pollution
 - injury
 - fungi
 - sweating
 - the skin
 - smoking


 

    injury     