## **Core Concept**
The lifespan of red blood cells (RBCs) is a critical aspect of transfusion medicine. Normally, RBCs have a lifespan of approximately 120 days in the human body. When RBCs are transfused, their lifespan can be affected by various factors including storage conditions, the age of the cells at the time of transfusion, and the recipient's health status.

## **Why the Correct Answer is Right**
Transfused RBCs have a maximum lifespan that is generally considered to be around 120 days, similar to native RBCs. However, the actual lifespan of transfused RBCs can be shorter due to factors like storage lesions and the recipient's immune response. The storage lesion refers to the changes that occur in RBCs during storage, which can affect their function and survival. Despite these factors, the maximum lifespan of transfused RBCs does not exceed 120 days.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option suggests a significantly shorter lifespan, which might reflect the average lifespan of transfused RBCs considering storage lesions and immune responses but does not represent the maximum possible lifespan.
- **Option B:** This option suggests a slightly longer lifespan but still underestimates the generally accepted maximum lifespan of RBCs.
- **Option D:** This option overestimates the lifespan, as RBCs, whether native or transfused, do not live longer than 120 days under normal circumstances.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that while the average lifespan of transfused RBCs might be less than 120 days due to various factors, the maximum lifespan does not exceed 120 days. This knowledge is crucial in transfusion medicine for managing patients requiring chronic transfusions and understanding the potential complications.

## **Correct Answer:** C. 120 days.