A) A-immune system, B-allergic reactions, C-histamine, D-serotonin
B) A-bone marrow, B-allergic reactions, C-mucous, D-cerumen
C) A-thymus, B-allergic reactions, C-histamine, D-cerumen
D) A-immune system, B-allergic reactions, C-cerumen, D-serotonin
Explanation
A-Immune system, B-Allergic reactions, C-Histamine, D-Serotonin