A. <span>Exposure to an antigen
Exposure to viruses and antigens led to the foundation of modern vaccination. Vaccination introduces an antigenic material that helps the ability of the immune system to adapt a specific pathogen, therefore leading to a long-term immunity.</span>
Answer: Option C) Reduction is the gain of electrons.
Explanation:
Reduction is a process involving a gain of electron(s), while oxidation involves a loss of electron(s).
Thus, an oxidizing agent is a substance that accepts electron(s) and become reduced, while a reducing agent is a substance that donates electron(s) and so becomes oxidized.
Thus, reduction is the gain of electron(s)
Everything in the universe was created when the Big Bang occurred and the universe is expanding
