Which of the following is required for M. tuberculosis to be virulent?

Tuberculosis can be especially difficult to treat for which of the following reasons?

I. It is slow-growing. 

II. Multi-drug-resistant strains are becoming more common.

III. The presence of mycolic acid and cord factor in the cell wall.

The exact progression of tuberculosis can vary based on the individual. For individuals that progress to severe disease, which of the following orders the stages of a tuberculosis infection correctly as most commonly experienced?

Which of the following statements about tuberculosis tubercles is correct?