Which of the following is NOT one of the eight known B vitamins?

B8, or Inositol, is not classified as one of the eight known B vitamins. The standard B vitamin complex includes B1 (Thiamine), B6 (Pyridoxine), B12 (Cobalamin), and five others: B2 (Riboflavin), B3 (Niacin), B5 (Pantothenic acid), B7 (Biotin), and B9 (Folate). While inositol is often discussed in the context of health and nutrition due to its role in cellular processes and potential health benefits, it does not meet the criteria of being an officially recognized B vitamin.

This distinction is important because the B vitamins collectively play crucial roles in energy metabolism, the nervous system, and various other physiological functions. Understanding the differences among these nutrients helps in appreciating their respective contributions to human health and nutrition.