Explanation:

- Urochrome:

- The correct answer is that urine is yellow primarily because of a pigment called urochrome. It is a byproduct of the breakdown of hemoglobin from red blood cells.

- Potassium:

- Potassium is an essential mineral that helps with nerve function and muscle contraction. It does not affect urine color.

- Endorphin:

- Endorphins are neurotransmitters in the brain that relieve pain and induce feelings of pleasure. They do not influence urine color.

- Insulin:

- Insulin is a hormone that regulates blood glucose levels. It does not change the color of urine.