Which among the following acts as a vitamin?

Which vitamin deficiency causes the disease known as scurvy?

Which of the following $B$-complex vitamins is stored in our body?

The metal ion present in vitamin $B_{12}$ is

Which of the following vitamins is not soluble in water?

Which of the following statements are correct?
$a$. Deficiency of vitamin $K$ results in increased blood clotting time.
$b$. The sources of vitamin $B_2$ are milk and liver.
$c$. Hexapeptide has six peptide bonds.
$d$. Improper functioning of adrenal cortex results in hypoglycemia.