Bone marrow and thymus are primary lymphoid organs where immature lymphocytes differentiate into antigen-sensitive lymphocytes. They provide the essential micro-environment for the development and maturation of B-lymphocytes (in the bone marrow) and T-lymphocytes (in the thymus). However, they are not the sites of interaction of lymphocytes with antigens, which occurs in secondary lymphoid organs such as spleen and lymph nodes, nor do they function as filters for trapping microorganisms. Hence, only statements and are correct.

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