The best option that matches the description is poison. Option A is correct.
Poison is described as a general term for any substance that can cause harm or death when ingested, absorbed, inhaled, or injected into the body. It encompasses a wide range of substances, including toxins, chemicals, plants, and even some naturally occurring foods.
While toxins are harmful substances, they specifically refer to poisonous proteins produced by living organisms like bacteria, plants, and animals. Therefore, while all toxins are poisons, not all poisons are toxins.