**Core Concept**
Blood storage with CPD-A (Citrate-Phosphate-Dextrose-Adenine) is a method used to preserve the viability of red blood cells. CPD-A is a type of anticoagulant-preservative solution that extends the shelf life of blood by preventing hemolysis and maintaining cellular function.

**Why the Correct Answer is Right**
The addition of adenine in CPD-A helps to maintain the ATP levels in red blood cells, which is crucial for maintaining their viability and function. Adenine is converted to ATP within the red blood cells, thereby reducing the loss of ATP and prolonging the storage time. This is particularly important for blood stored for transfusion, as fresh red blood cells are essential for maintaining adequate oxygen delivery to tissues.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because CPD-A is specifically designed for whole blood storage, not for component storage like packed red blood cells.
**Option B:** This option is incorrect because CPD-A is not suitable for long-term storage of blood; it is designed for storage up to 35 days.
**Option C:** This option is incorrect because CPD-A is specifically designed for whole blood storage, not for platelet storage.

**Clinical Pearl / High-Yield Fact**
The addition of adenine to CPD-A is a critical component in maintaining the viability of red blood cells during storage. It is essential to note that blood stored with CPD-A should not be used beyond 35 days, as the risk of hemolysis and cellular dysfunction increases significantly after this period.

**Correct Answer:** B. 35 days