This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
All are peripheral lymphoid organs except ? 
Select and explain. 
A. Lymph nodes, B. Spleen, C. Mucosa associated lymphoid tissue, D. Thymus
D: Thymus
Answer: D: Thymus 
Explanation: Ans. is 'd' i.e., Thymus Lymphoid system . The lymphoid system consists of all of the tissue aggregates and organs composed of lymphoid tissue which function together to produce specific resistance to immunity. . The lymphoid organs are divided into. Remember . Bone marrow acts as central as well as peripheral lymphoid organ. . Spleen is the largest lymphoid organ. . Thymus is the first organ to become predominantly lymphoid.