Which one of the following statements is correct?

Which one of the following statements is correct?

Urea is produced in liver.
Urea is produced in blood.
Urea is produced from digestion of starch.
Urea is produced in lung and kidney.
This question was previously asked in
UPSC CDS-1 – 2019
The correct answer is A. Urea is the principal nitrogenous waste product in humans and other mammals. It is synthesized in the liver through a metabolic pathway known as the urea cycle (or ornithine cycle). This process converts ammonia, a toxic byproduct of protein metabolism, into less toxic urea. Urea is then released into the bloodstream and transported to the kidneys for excretion in urine.
Urea is primarily synthesized in the liver through the urea cycle.
Amino acids from dietary protein are broken down in the liver, producing ammonia. The urea cycle combines ammonia with carbon dioxide to form urea. The kidneys filter urea from the blood, concentrating it in urine for elimination from the body. The lungs are involved in gas exchange (oxygen and carbon dioxide), and the digestion of starch yields glucose, not urea.