The correct option is A 50%
The mucosa-associated lymphoid tissue (MALT), is a diffused system of small amounts of secondary lymphoid tissue found in the mucosal lining of the gastrointestinal tract, respiratory tract and urogenital tract.
It constitutes about 50% of the lymphoid tissue in the human body.
MALT is rich in lymphocytes such as T cells (produced in bone marrow but mature in the thymus), B cells (produced in bone marrow and also mature in the bone marrow), macrophages (phagocytic cells that can engulf and digest foreign bodies), etc. to fight with antigens passing through the mucosal epithelium.