Small secondary lymphoid organs, which cluster along lymphatic vessels, are termed

Lymph nodes. They comprise the lymphatic system that connects to the blood circulatory system.  They are significant in the immune system. At the lymph nodes, foreign bodies in the lymph, such as pathogens, are filtered and trapped in lymph nodes where they are later destroyed by lymphocytes.

b

explanation:

it's anything that aren't producers and consumers.

explanation:

you've got to be clear on what "this" is