**Core Concept**
Bone marrow biopsy in infants poses a challenge due to the small size of their bones and the high risk of complications. The procedure requires careful consideration of the safest and most effective site for sampling.

**Why the Correct Answer is Right**
In infants, the iliac crest is not yet fully developed, making it an unsuitable site for bone marrow biopsy. However, the sternum, specifically the proximal part of the sternum, provides a suitable site for bone marrow aspiration and biopsy in infants. This is because the sternum is larger in infants and has a more developed marrow cavity, allowing for a safer and more effective sampling procedure.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not provided, but typically, the iliac crest would be incorrect due to its underdeveloped state in infants.
* **Option B:** The iliac crest is not suitable for bone marrow biopsy in infants due to its small size and underdeveloped state.
* **Option C:** This option is not provided, but typically, the lumbar vertebrae would be incorrect due to the risk of spinal injury and the difficulty of accessing the marrow cavity in infants.
* **Option D:** This option is not provided, but typically, the femur would be incorrect due to its small size and the difficulty of accessing the marrow cavity in infants.

**Clinical Pearl / High-Yield Fact**
In infants, the sternum is a suitable site for bone marrow biopsy due to its larger size and more developed marrow cavity, allowing for a safer and more effective sampling procedure.

**Correct Answer:** C.