Type III secretion systems are used to inject "effector" proteins directly into a host cell. Salmonella uses a type III secretion system to help the pathogen to

• A. survive the acid pH of the stomach
• B. secrete LT (heat labile toxin) and ST (heat stable toxin) into the lumen of the intestine
• C. survive within macrophages
• D. activate T cells to proliferate and secrete cytokines