This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of carbohydrate, Subject name: Biochemistry
The molecule, which is the initiator of cataract formation in the eye lens and whose 1-phosphate derivative is responsible for liver failure, is 
Select and explain. 
A. Sorbitol, B. Mannitol, C. Inositol, D. Galactitol
D: Galactitol
Answer: D: Galactitol 
Explanation: In lens, the enzyme aldose reductase reduces monosaccharides to corresponding sugar alcohols; glucose to sorbitol and galactose to galactitol.these polyols do not cross cell membranes and hence accumulate; causing osmotic swelling and consequent disruption of cell architecture. Thus diabetes mellitus and galactosemia cause cataractRef: DM Vasudevan, 7th edition, page no: 727