Which of the following best describes the composition of urine?

The composition of urine is primarily water and urea, making it the most accurate description among the options provided. Urine is made up of approximately 95% water, which serves as a solvent for the waste products the kidneys filter from the blood. Urea, a byproduct of protein metabolism, is one of the main waste substances excreted in urine. This natural process helps the body eliminate excess nitrogen while conserving vital nutrients and maintaining homeostasis.

The other options describe elements that are not predominant in urine. For instance, urine does not have a high concentration of protein and fats, as the kidneys normally filter these components effectively to prevent their loss. Similarly, while glucose and amino acids can appear in urine under certain pathological conditions, they are generally reabsorbed in the kidneys and are not a significant part of normal urine composition. Lastly, while minerals and electrolytes do exist in urine in trace amounts, they are not the primary constituents. Therefore, describing urine as primarily water and urea accurately reflects its composition and function in the body.