Treatment of multiple carboxylase deficiency –: (A) Biotin, (B) Pyridoxine, (C) Thiamine, (D) Folic acid
Answer is A. Pathogenesis of multiple carboxylase deficiency 

Deficiency of either holocarboxylase synthase or biotinidase impaires biotin metabolism.
Biotin is a cofactor for various carboxylases in the body -
Impaired metabolism of biotin results in multiple carboxylase deficiency.
So, for the treatment of multiple carboxylase deficiency, biotin should be given.