Spongy or cancellous bones are

Options

A. skull bones
B. vertebrae
C. femur
D. ribs

Answer

**Step-by-Step Solution:**

1. **Understanding Spongy or Cancellous Bones:**
- Spongy bones, also known as cancellous bones, are characterized by their porous structure. They are less dense than compact bones and contain many small cavities or pores.

2. **Identifying Characteristics:**
- These bones are highly vascularized, meaning they have a rich blood supply. They also contain red bone marrow, which is important for blood cell production.

3. **Location of Spongy Bones:**
- Spongy bones are typically found at the ends of long bones, specifically in areas known as the epiphyses. This is crucial for understanding where these bones are located in the body.

4. **Evaluating the Options:**
- Now, let’s evaluate the options provided:
- **Skull Bones:** Generally consist of compact bone and do not primarily contain spongy bone.
- **Vertebrae:** These do contain spongy bone, but they are not long bones.
- **Femur:** This is a long bone and contains spongy bone at its ends (epiphyses).
- **Ribs:** While they have some spongy bone, they are not classified as long bones.

5. **Conclusion:**
- The best answer to the question "Spongy or cancellous bones are" is the **femur**, as it is a long bone that contains spongy bone at its ends.

**Final Answer:**
- The correct option is **third: femur**.

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