Contaminated lands and environments cause health difficulties such as cancer, can effect the respiratory system, and problems on the skin.
Answer:
Exposure to the disease
Explanation:
Before vaccines, the only way to develop immunity to a disease was to be exposed to the disease-causing pathogen without being harmed by it. A good example of this is smallpox, which was also the first vaccine developed. It was noticed that milk maids weren't catching and dying from small pox like everyone else, because they had been exposed to cowpox. This premise was used to create the first vaccine.
Vaccines give you immunity by injecting you with a small amount of a (usually inactive) pathogen. inside your body. This means your immune system produces antibodies against it. Similar to what happened with the milkmaids.
The answer is true.
<span>Antigens are molecules capable to induce an immune response, "targeted" by antibodies. Antigens are usually proteins, peptides, or polysaccharides but they can combine with lipids and nucleic acids and form more complex antigens (lipopolysaccharide). Usually, antigens are exogenous (foreign substances), but sometimes are part of the host itself (in an autoimmune disease). All of them contain an epitope which is a part of an antigen that can be recognized and bound by an antibody.</span>
They can tell about maybe what they looked like, where they were common, or how they were formed
