This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Cataract in galactosemia is caused by accumulation of: 
Select and explain. 
A. Sorbitol, B. Galactitol, C. Galactose, D. None of the above
B: Galactitol
Answer: B: Galactitol 
Explanation: Inability to metabolize galactose occurs in the galactosemia, which may be caused by inherited defects of galactokinase, uridyl transferase, or 4-epimerase, though deficiency of uridyl transferase is the best known. Galactose is a substrate for aldose reductase, forming galactitol, which accumulates in the lens of the eye, causing cataract. Ref: Harper 28th edition, chapter 21.