The correct option is A reject a tissue transplant
The thymus is a specialized primary lymphoid organ of the immune system. Within the thymus, T-cells mature. T-cells are critical to the adaptive immune system, where the body adapts specifically to foreign invaders. The thymus is the largest and most active during the neonatal and pre-adolescent periods. Removal of the thymus results in immunodeficiency because T-cells do not undergo maturation and this results in suppression of the immune system. Hence, a person without thymus would not be able to reject a tissue transplant because T-cells are suppressed.