You are presented with the quiz "What can make lungs more at risk for infection by streptococcus?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "pneumonia may be caused by an infection or injury of the lungs" and "streptococcal pneumonia is caused by the bacteria Streptococcus pneumoniae". 

So, what's the best answer to the question?


 

    injury       