$A$ metal present in vitamin $B_{12}$ is

The deficiency of which vitamin causes pernicious anaemia?

Which of the following is a water-soluble vitamin?

Identify a natural source of ascorbic acid from the following.

Which of the following biomolecules contains a non-transition metal ion?

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.