Final answer:
MALT refers to lymphatic tissue associated with mucosal surfaces except for the thymus, which is a primary lymphoid organ involved in T-cell maturation.
Step-by-step explanation:
Mucosa-associated lymphoid tissue (MALT) refers to the collection of lymphatic tissue that combines with epithelial tissue lining the mucosa throughout the body. Important components of MALT include tonsils, Peyer's patches in the small intestine, and the appendix. Unlike these, the thymus is not associated with mucosal tissues but is rather a primary lymphoid organ situated in the upper chest, where it plays a role in T-cell maturation. Therefore, the correct answer to the question is 'c. Thymus'.