## **Core Concept**
In infants, the bone marrow is primarily located in the **spongy bones** and **flat bones** due to the high proportion of red marrow. The **iliac crest** is a common site for bone marrow biopsy in adults, but in infants, the site differs due to the anatomy and accessibility.

## **Why the Correct Answer is Right**
The correct answer, **.**, corresponds to the **tibia**. In infants, the **tibial bone marrow** is a preferred site for bone marrow biopsy. This is because the tibia is easily accessible and has a high concentration of bone marrow. The procedure involves inserting a needle into the tibia to collect a bone marrow sample, which can help diagnose various conditions such as leukemia, infection, or blood disorders.

## **Why Each Wrong Option is Incorrect**
* **Option A:** - This option is incorrect because, although the **sternum** does contain bone marrow, it is not the preferred site for bone marrow biopsy in infants due to its location and accessibility.
* **Option B:** - This option is incorrect because the **iliac crest** is a common site for bone marrow biopsy in adults, not typically used in infants due to the differences in bone marrow distribution and accessibility.
* **Option C:** - This option is incorrect because, although **flat bones** like the **ribs** or **skull** do contain bone marrow, they are not the preferred sites for routine bone marrow biopsy in infants.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that in infants, the **tibia** is a safe and effective site for bone marrow aspiration and biopsy. This is particularly useful in diagnosing conditions that affect the bone marrow, such as **severe combined immunodeficiency** or **leukemia**.

## **Correct Answer:** . Tibia