Which solution is isotonic to the blood?

Options

A. 0.75% by weight of NaCl approximately
B. 0.99% by weight of NaCl approximately
C. 0.90% by weight of NaCl approximately
D. None of these

Explanation

To determine which solution is isotonic to blood, we need to understand the concept of isotonic solutions and their osmotic pressure.

### Step-by-Step Solution:

1. **Definition of Isotonic Solutions**:
- Isotonic solutions are solutions that have the same osmotic pressure as another solution, in this case, blood. This means that when cells are placed in an isotonic solution, there will be no net movement of water into or out of the cells, maintaining their shape and function.

2. **Identifying the Isotonic Solution**:
- The most commonly known isotonic solution for human blood is a saline solution. Specifically, a 0.9% sodium chloride (NaCl) solution is recognized as isotonic to blood.

3. **Importance of Concentration**:
- It is crucial to use the correct concentration of NaCl. If a solution with a concentration lower than 0.9% NaCl is used, it can cause cells to swell due to water influx (hypotonic). Conversely, a higher concentration can lead to cell shrinkage due to water loss (hypertonic).

4. **Conclusion**:
- Therefore, the solution that is isotonic to blood is a 0.9% NaCl solution.

### Final Answer:
- **0.9% NaCl solution is isotonic to blood.**