The pathogenicity of the tubercle bacillus is due to which ONE of the following?

The answer is B. Mycobacteria stimulate a specific T-cell response of cell mediated immunity; while this is effective in reducing the infection the delayed hypersensitivity reaction also damages the tissues. The tubercle bacilli have no demonstrable direct toxic action (C) and can survive within macrophages (A). This may account for latent infections and reactivation of tuberculosis. There is no significant humoral response to tubercle bacilli (D). Necrosis occurs in tuberculosis, but it is usually within the granuloma (E).