Which of the vitamins given below is water soluble?

First, let us recall the basic classification of vitamins. Vitamins are generally grouped into two broad categories based on their solubility:

1. Water-soluble vitamins       2. Fat-soluble vitamins

Water-soluble vitamins dissolve readily in water, circulate easily through the bloodstream, and are not stored in large amounts in the body. Hence, any excess is usually excreted in urine. On the other hand, fat-soluble vitamins dissolve in fats and oils, are absorbed along with dietary lipids, and can be stored in the liver and adipose tissues.

Now, we list the well-known members of each group:

Water-soluble: Vitamin $$B_1$$ (thiamine), $$B_2$$ (riboflavin), $$B_3$$ (niacin), $$B_5$$ (pantothenic\;acid), $$B_6$$ (pyridoxine), $$B_{12}$$ (cobalamin), biotin, folic acid, and Vitamin C (ascorbic acid).

Fat-soluble: Vitamins A, D, E, and K.

Observing the given options, we have:

Option A   Vitamin K  →  fat-soluble

Option B   Vitamin C  →  water-soluble

Option C   Vitamin D  →  fat-soluble

Option D   Vitamin E  →  fat-soluble

We see that only Vitamin C belongs to the list of water-soluble vitamins.

Hence, the correct answer is Option B.