What are Vitamins and give the classification of Vitamins

Question

$\begin{array}{1 1} \text{(a) Vitamins are classified as either soluble or insoluble.} \\ \text{(b)Vitamins are classified as either water-soluble or fat-soluble.} \\ \text{(c) Vitamins are classified as metallic Vitamins, non-metallic Vitamins.} \\ \text{(d)Vitamins are classified as either simple or Conjugate}\end{array}$