A autosomal recessive disorder caused by mutation in SLC19A2 gene and characterized by megaloblastic anemia, diabetes mellitus and sensorineural hearing loss. This child responds to which nutrient: (A) Vitamin B12, (B) Vitamin c, (C) Vitamin B1, (D) Folic acid
Answer is C. This is Thiamine Responsive Megaloblastic syndrome:

It occurs due to mutation of SLC19A2 gene, encoding thiamine transporter protein, Leading to abnormal thiamine transportation.

Clinical features:

Megaloblastic anemia
Diabetes mellitus
Sensorineural hearing loss.