A newborn infant refuses breast milk since the 2nd day of birth,vomits on force-feeding but accepts glucose-water,develops diarrhea on the third day,by 5th day she is jaundiced with liver enlargement and eyes show signs of cataract.Urinary reducing sugar was positive but blood glucose estimated by glucose oxidation method was found low.The most likely cause is deficiency of:

• A. Galactose-1-phosphate uridyl transferase
• B. Beta galactosidase
• C. Glucose-6-phosphatase
• D. Galactokinase