Answer: The term that describes any substance that the body regards as foreign is "antigens" (Option B).
Step-by-step explanation:
Antigens are molecules or substances that are recognized by the immune system as non-self or foreign. They can include molecules from pathogens such as bacteria, viruses, fungi, and parasites, as well as non-infectious substances like pollen, certain foods, drugs, and even transplanted tissues or organs.
When antigens enter the body, they trigger an immune response. The immune system recognizes these antigens as foreign and initiates a series of defensive mechanisms to neutralize or eliminate them. This response involves the production of specific proteins called antibodies (Option A), which bind to the antigens and mark them for destruction.
Pathogens (Option C) are disease-causing agents such as bacteria, viruses, fungi, and parasites. While many pathogens carry antigens, the term "antigens" is broader and encompasses any substance that is recognized as foreign by the immune system.
Antivirals (Option D) are medications used to treat viral infections. They work by inhibiting the replication of viruses within the body. Although they can be effective against specific viruses, antivirals are not substances that the body regards as foreign like antigens.
In summary, the term that describes any substance that the body regards as foreign is "antigens." Antigens can include molecules from pathogens, as well as non-infectious substances, and they trigger an immune response in the body.