Consider the following water conservation mechanisms:
(a) Nasal countercurrent mechanism
(b) Dependence on metabolic water
(c) Highly hypertonic urine
(d) Living more on protein rich diet.
A kangaroo rat living in desert can survive without drinking water because of

Options

A. (a) (a), (b) and (c)
B. (b) (a), (b) and (d)
C. (c) (b), (c) and (d)
D. (d) (a), (c) and (d)

Answer

To determine how a kangaroo rat can survive in the desert without drinking water, we need to analyze the provided water conservation mechanisms one by one.

### Step-by-Step Solution:

1. **Nasal Countercurrent Mechanism (Option a)**:
- The kangaroo rat has a specialized nasal structure that allows it to conserve water. The nasal passages have a countercurrent mechanism where the inhaled air and exhaled air flow in opposite directions. This mechanism cools the exhaled air, reducing water loss during respiration.
- **Conclusion**: This mechanism helps in minimizing water loss, making it a valid adaptation for survival in the desert.

2. **Dependence on Metabolic Water (Option b)**:
- Kangaroo rats rely on metabolic water, which is produced during cellular respiration. This means they can derive sufficient water from the breakdown of food, particularly from carbohydrates and fats, reducing their need for external water sources.
- **Conclusion**: This is also a true adaptation, allowing kangaroo rats to survive without drinking water.

3. **Highly Hypertonic Urine (Option c)**:
- The kangaroo rat produces highly concentrated urine, which is a method of conserving water. By excreting urine that is hypertonic (more concentrated than the body fluids), they can retain more water in their bodies while still eliminating waste.
- **Conclusion**: This adaptation is effective in preventing water loss, making it a true mechanism for survival.

4. **Living More on Protein Rich Diet (Option d)**:
- While protein-rich diets can lead to higher ammonia production, kangaroo rats are uricotelic, meaning they excrete uric acid instead of urea. Uric acid is less toxic and requires less water for excretion. However, the statement implies that a protein-rich diet is beneficial for water conservation, which is misleading in the context of their adaptations.
- **Conclusion**: This statement is false as it does not align with the kangaroo rat's primary adaptations for water conservation.

### Final Conclusion:
The correct mechanisms that allow the kangaroo rat to survive without drinking water are:
- (a) Nasal countercurrent mechanism
- (b) Dependence on metabolic water
- (c) Highly hypertonic urine

Thus, the answer is that the kangaroo rat survives without drinking water due to mechanisms (a), (b), and (c).