Question

1. what does a vaccine contain?

t cells
infectious particles
antigens
antibodies

Explanation:

A vaccine contains antigens. Antigens are substances that can trigger an immune response. Vaccines use weakened, dead, or parts of pathogens (which have antigens) to stimulate the body to produce antibodies and memory cells (like T - cells and B - cells) for future protection. T - cells are part of the immune response that is triggered after vaccination, not what the vaccine contains. Infectious particles in a harmful form would cause disease, and vaccines do not contain harmful infectious particles in most cases (except for some live - attenuated vaccines which are in a weakened form but still, the key component is the antigen). Antibodies are produced by the body in response to the antigen in the vaccine, not present in the vaccine itself.

Answer:

antigens