Normal saline solution is

Options

A. 1 N salt solution
B. 0.9% mass/volume NaCI solution
C. 1 N NaCI solution
D. Normal salt solution

Answer

To determine what a normal saline solution is, we can analyze the options given and understand the composition of a saline solution.

### Step-by-Step Solution:

1. **Understanding Normal Saline Solution**:
- A normal saline solution is typically a solution of sodium chloride (NaCl) in water. The standard concentration for normal saline is 0.9% (mass/volume).

2. **Analyzing the Options**:
- **Option A**: "One normal salt solution" - This refers to a solution with a concentration of 1 equivalent of solute per liter, which is not the same as normal saline.
- **Option B**: "0.9% mass per unit volume NaCl solution" - This indicates that 9 grams of NaCl is dissolved in 1000 mL of water, which matches the definition of normal saline.
- **Option C**: "One normal NaCl solution" - This indicates a solution where 1 equivalent of NaCl is dissolved in 1000 mL of water, which is not the same as normal saline.
- **Option D**: "Normal salt solution" - This is too vague and does not specify the concentration, making it an incorrect option.

3. **Identifying the Correct Option**:
- Since the definition of normal saline is a 0.9% NaCl solution, the correct answer is **Option B**: "0.9% mass per unit volume NaCl solution".

### Conclusion:
The normal saline solution is a 0.9% (mass/volume) NaCl solution, which means 9 grams of NaCl is dissolved in 1000 mL of water.

---