What is Rh factor ?

Explanation

### Step-by-Step Solution:

1. **Definition of Rh Factor**: The Rh factor, also known as the Rhesus factor, is a specific protein that can be present on the surface of red blood cells (RBCs).

2. **Presence and Absence**: If the Rh factor is present on the RBCs, the blood type is classified as Rh positive (e.g., A+, B+, AB+, O+). Conversely, if the Rh factor is absent, the blood type is classified as Rh negative (e.g., A-, B-, AB-, O-).

3. **Importance in Blood Transfusion**: The Rh factor is crucial in blood transfusions. Individuals with Rh positive blood can receive blood from both Rh positive and Rh negative donors. However, individuals with Rh negative blood can only receive blood from Rh negative donors to avoid potential immune reactions.

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