Answer:
a. Make antibodies
Explanation:
B-cells is one of the two types of lymphocytes or white blood cells produced in the marrow of the bone (the other being T-cells). B-cells are a part of adaptive or acquired immunity in our body i.e. a learned defense after a pathogen might have penetrated.
B-cells help combat foreign Invaders that make way into the body by producing ANTIBODIES, which are specific to a particular pathogen. Note that, the B-cells learnt to combat based on a previous infection of such pathogen. In response to an antigen, the B-cells produce the plasma cells, which in turn produce the antibodies.