D.

Odontoblast

The pulp cavity contains a mass of dense but soft connective tissue which is called pulp. A single layer of odontoblast cells lines the pulp cavity. These cells secrete enamel, which is a bluish-white shiny translucent and the hardest substance of the body.

B.

Simple diffusion

Oxygen diffuses from alveoli to deoxygenated blood, and carbon dioxide diffuses from deoxygenated blood to alveoli by simple diffusion. Diffusion is defined as, the flow of the substance (gases) from a region of their higher concentration to a region of lower concentration.

C.

Reacts with haemoglobin

Carbon monoxide, when inhaled, combines with blood haemoglobin to form carboxyhaemoglobin at a rate 210 times faster than the rate of oxygen forms oxyhaemoglobin. Thus, respiration is impaired.

B.

Lowers calcium level in a blood

Calcitonin is a polypeptide hormone which lowers calcium and phosphate levels of plasma by inhibiting bone degradation and stimulating their uptake by bone. Parathyroid hormone elevates calcium level in blood.

C.

Anuria

The terms anuria, oligonuria, polynuria and dysuria are used for the absence of urine, scanty urine, large amounts of urine, and painful urination respectively. Deamination is the removal of amino (NH) group frequently from an amino acid by transaminase enzymes.