20. Type 1 fucosidosis is a rare buman disease. Patients cannot hydrolyze the disaccharide fucose, and as a result have severe neurological decline and die by age 6. The disease is due to a defect in the gene that encodes the lysosomal enzyme that breaks down fucose (α-1-fucosidase), and is inherited in an autosomal recessive manner. Jane and John have a child who has Type 1 fucosidosis. What is the probability that their next two children will all NOT have the disease?
(A) None (all of their children will have the disease)
(B) 1/2
(C) 3/4
(D) 1/8
(E) 9/16