instruction:
Given a scientific question, generate a correct answer to it.
question:
Despite its small size, an erythrocyte contains about 250 million molecules of what?
answer:
hemoglobin

question:
Activated macrophages and neutrophils discharge what that signals molecules that enhance an immune response?
answer:
cytokines

question:
The type of what dictates how far it can penetrate into matter, such as lead or human flesh?
answer:
radiation