Given below are two statements. One is labelled Assertion (A) and the other is labelled Reason (R).  

Assertion (A): The thymus plays a role in the development of the immune system. 

Reason (R): Thymosins play a major role in the differentiation of B-lymphocytes. 

In the light of the above statements, choose the most appropriate answer from the options given below.

The thymus plays a major role in the development of the immune system. This gland secretes the peptide hormones called thymosins. Thymosins play a major role in the differentiation of T-lymphocytes, which provide cell-mediated immunity. In addition, thymosins also promote production of antibodies to provide humoral immunity. Thymosins do not influence the maturation of B-lymphocytes.