Red blood cells (RBC) are isotonic with ……………..`%NaCl` solution.

Explanation

To determine the percentage of NaCl solution that is isotonic with red blood cells (RBC), we can follow these steps:

### Step-by-Step Solution:

1. **Understand Isotonic Solutions**:
Isotonic solutions have the same osmotic pressure, which means they have the same concentration of solute particles. For red blood cells, this means that the osmotic pressure of the NaCl solution must equal that of the RBCs.

2. **Identify the Osmotic Pressure Formula**:
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