Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): The thymus is quite large at the time of birth but keeps reducing in size with age, becoming very small by puberty. Reason (R): It is a secondary lymphoid organ that loses its function once the acquired immune system is fully developed. In the light of the above statements, choose the most appropri

Step-by-step solution

The Assertion is a correct statement. According to NCERT, the thymus is quite large at the time of birth but keeps reducing in size with age and by the time puberty is attained it reduces to a very small size. The Reason is an incorrect statement. The thymus is a primary lymphoid organ, not a secondary lymphoid organ. Primary lymphoid organs (bone marrow and thymus) are the sites where immature lymphocytes differentiate into antigen-sensitive lymphocytes. Therefore, Assertion (A) is true but Reason (R) is false. An