The correct option is B If both assertion and reason are true but reason is not the correct explanation of assertion
Artificially acquired passive immunity results when antibodies or lymphocytes that have been produced outside the host are introduced into a host. This type of immunity is immediate, short lived, lasting only a few weeks to a few months.
When the immune system is compromised and looses its ability to fight infectious diseases due external or genetic factors, it is called immunodeficiency.
Bone marrow transplant is given to a patient with genetic immunodeficiency. Here, the stem cells are being transplanted which gives rise to the lymphocytes or antibodies inside the patient. So, it can be considered as artificial passive immunity.