B: Antigens
Explanation: Antigens itself are the invaders that causes an infection or a disease in living organism. They do not protect against invaders in non-specific response as they themselves are the ones who are invading the body.
Digestive enzymes are the enzymes that act on a particular substrate for its action at a particular PH.
Stomach acid is the hydrochloric acid that keeps the PH of the stomach low and prevents the growth of unwanted pathogens.
Lysosomes have digestive enzymes in it. It performs the process of phagocytosis.