Considering vitamin classification, is vitamin B12 a fat soluble vitamin or a water soluble vitamin?

Introduction / Context:
Vitamins are often grouped into fat soluble and water soluble categories. Knowing which vitamins fall into each group is important in nutrition, because it affects how they are absorbed, stored and excreted by the body. This question tests whether you correctly identify vitamin B12 as belonging to the water soluble group rather than the fat soluble group.

Given Data / Assumptions:

• Fat soluble vitamins usually include vitamins A, D, E and K.
• Water soluble vitamins generally include the B complex vitamins and vitamin C.
• Vitamin B12 is also known as cobalamin and is part of the B complex group.

Concept / Approach:
Vitamins that dissolve in fat can be stored in body fat and the liver for longer periods, while water soluble vitamins dissolve in water and are not stored to the same extent. The B complex group, including B1, B2, B3, B6, B9 and B12, is classified as water soluble. Vitamin B12 is essential for red blood cell formation and proper functioning of the nervous system, but in classification it remains a water soluble vitamin, even though the body can store it in the liver for some time.

Step-by-Step Solution:
Step 1: Recall the two main groups of vitamins, fat soluble and water soluble. Step 2: Remember that fat soluble vitamins are A, D, E and K. Step 3: Recognise that all B vitamins, including vitamin B12, and vitamin C are water soluble. Step 4: Connect vitamin B12 with the B complex group and classify it as water soluble. Step 5: Select the option that clearly states that vitamin B12 is a water soluble vitamin.

Verification / Alternative check:
Nutrition texts and medical references consistently list vitamin B12 among the water soluble vitamins. Although vitamin B12 can be stored in body tissues for long periods, this storage behaviour does not change the chemical classification. All B vitamins are water soluble by definition, in contrast to fat soluble vitamins that are mainly A, D, E and K.

Why Other Options Are Wrong:
Option a incorrectly labels vitamin B12 as fat soluble, which is reserved for A, D, E and K.

Option c suggests that it is both fat and water soluble, which does not match standard vitamin classification.

Option d states that it is neither fat nor water soluble, which is impossible because every vitamin must dissolve in some medium and B12 clearly dissolves in water.

Common Pitfalls:
Learners sometimes get confused because vitamin B12 can be stored in the liver for years, which feels similar to fat soluble vitamin storage. They may then incorrectly assume that B12 is fat soluble. It is important to keep the chemical classification separate from storage duration and remember that B vitamins remain water soluble even if some are stored efficiently.

Final Answer:
Vitamin B12 belongs to the group of water soluble vitamins.