Differentiate between the following pairs on the basis of what is mentioned within brackets :
RBC and WBC (Shape)

Explanation

### Step-by-Step Solution:

1. **Definition of RBC and WBC**:
- RBC stands for Red Blood Cells, also known as erythrocytes.
- WBC stands for White Blood Cells, also known as leukocytes.

2. **Shape of RBC**:
- RBCs are characterized by their **biconcave disc shape**. This means they have a round shape that is indented on both sides, resembling a doughnut without a hole.
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