$A$ person has "bleeding gum" problem. Which of the following vitamin deficiency may be the reason for it?

Vitamin $B_1$ is

Which of the following acids is a vitamin?

Ascorbic acid is a

Assertion : Vitamin $D$ cannot be stored in our body.
Reason : Vitamin $D$ is a fat-soluble vitamin and is excreted from the body in urine.

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.