Spongy (cancellous) bone differs from compact (dense) bone in that spongy bone :

Options

A. has a concentric-ring structure
B. is found primarily in the diaphyses of long bones
C. contains many large cavities
D. is made up of numerous osteons (Haversian systems)

Explanation

### Step-by-Step Solution:

1. **Definition of Bone Types**:
- Understand that there are two main types of bone tissue: spongy (cancellous) bone and compact (dense) bone.

2. **Characteristics of Spongy Bone**:
- Spongy bone is also known as cancellous bone.
- It is lighter and has a softer texture compared to compact bone.
- It is composed of a network of trabeculae (small rod-like structures).
- Spongy bone is found in the inner layer of bones, particularly at the ends of long bones.

3. **Characteristics of Compact Bone**:
- Compact bone is also referred to as cortical bone.
- It is denser, heavier, and tougher than spongy bone.
- Compact bone is made up of osteons (the structural unit of compact bone).
- It forms the outer layer of bones and is primarily found in the diaphysis (shaft) of long bones.

4. **Presence of Cavities**:
- Spongy bone contains a large number of cavities, which contribute to its lighter structure.
- In contrast, compact bone does not have these large cavities.

5. **Bone Marrow Cavity**:
- The bone marrow cavity is absent in spongy bone.
- Compact bone, however, contains a bone marrow cavity.

6. **Conclusion**:
- Based on the characteristics discussed, spongy bone differs from compact bone primarily in that it has a structure characterized by many large cavities, is lighter, and is made up of trabeculae rather than osteons.

### Final Answer:
Spongy (cancellous) bone differs from compact (dense) bone in that spongy bone contains many large cavities.