The right answer is 3).
Lymph nodes are the place of proliferation and differentiation of immune cells. The primary role of the lymphatic vessels is to bring an antigen (in the vast majority of cases from a pathogen) from the tissue to the ganglia, to activate the specific immune response of T and B cells.
The fact that the circulation is slow favors the contact between the lymphocytes at the level of the ganglia and the antigens.