**Explanation:**

The pH of urine refers to its acidity or alkalinity. It is measured on a scale of 0 to 14, with 7 being considered neutral. Any pH value below 7 is acidic, while a pH above 7 is alkaline.

Under healthy conditions, the pH of urine is slightly acidic. The correct answer is option 'D'.

There are several factors that contribute to the slightly acidic pH of urine:

1. **Diet:** The foods and beverages we consume can affect the pH of urine. Diets high in protein and acidic foods can make the urine more acidic. On the other hand, diets rich in fruits and vegetables can make the urine more alkaline.

2. **Metabolism:** Metabolic processes in the body produce acidic byproducts that are excreted through urine. These include sulfuric acid, phosphoric acid, and uric acid. The presence of these acids contributes to the acidic nature of urine.

3. **Respiratory Regulation:** The body maintains acid-base balance through respiratory and renal regulation. Carbon dioxide, a waste product of metabolism, can be eliminated through the lungs or converted to bicarbonate ions by the kidneys. This bicarbonate acts as a buffer to maintain the pH of blood and urine.

4. **Renal Regulation:** The kidneys play a crucial role in maintaining the pH of urine. They selectively reabsorb or excrete ions and molecules to adjust the pH as needed. For example, hydrogen ions can be actively secreted into the urine to lower its pH.

Overall, the slightly acidic pH of urine under healthy conditions is a result of various metabolic processes, dietary factors, and renal regulation. It is important to note that the pH of urine can vary throughout the day and may be influenced by factors such as hydration levels, medications, and certain medical conditions.

The pH of urine under healthy conditions is slightly less than 7 so, slightly acidic in nature