Correct answer: (d) They protect the body from the diseases caused by pathogens.
Explanation
- A
They protect the body from environmental allergens.
Protect from environmental allergens. A slice of immunity (IgE), not the core B/T job as keyed.
- B
They alleviate the body's pain and inflammation.
Alleviate pain and inflammation. That is drugs / other mediators.
- C
They act as immunosuppressants in the body.
Act as immunosuppressants. Regulatory T cells modulate; they are not ‘the’ immunosuppressants.
- D
They protect the body from the diseases caused by pathogens.
Protect from diseases caused by pathogens. Adaptive immunity: B cells (antibodies) and T cells (cellular).
Summary. Official key is (d). B lymphocytes and T lymphocytes are the adaptive immune cells that defend against pathogens. Allergen handling, analgesia and immunosuppression are not their defining role in this item.