Krabbe disease is characterized by a deficient enzyme and accumulated substrate. What is the deficient enzyme and accumulated substrate, respectively?
a) Galactocerebrosidase, Galactocerebroside.
b) Arylsulfatase A, Sulfatide.
c) β-Glucocerebrosidase, Glucocerebroside.
d) β-Galactocerebrosidase, Galactocerebroside.