Answer:Primary lymphoid organs: These organs include the bone marrow and the thymus. They create special immune system cells called lymphocytes. Secondary lymphoid organs: These organs include the lymph nodes, the spleen, the tonsils and certain tissue in various mucous membrane layers in the body
if you were making an observation of two substances, The five conditions of chemical change would be color chage, formation of a precipitate, formation of a gas, odor change, temperature change. i hope this helps
